Many people have asked this question, and the most significant answer is simply because a Macintosh will not give you anywhere as much grief as a DOS box. Everything about a Macintosh is easier to use than Windows, even Windows 95. After all, as much as Microsoft tries to hide it with Windows 95, they're still DOS boxes. You still have to edit .INI files and putting a new video card in will still not work right, despite the claims of plug and play.
The proof is in the pudding though. Here's my 2 year old daughter Jordan booting her Macintosh. She's already inserted the Lion King CD, although knowing her, she'll tire of it as soon as she launches it and then she'll put in a new one. Nothing is as fickle as a two year old.
The significant part of this is that she can do it! In fact, she's already better than a lot of adults I know, although she hasn't had to save any files yet. That's always the first stumbling point for any Macintosh user. Then it's that RAM versus hard disk issue. Well, isn't it all memory? But I digress.
The thing I can't really prove is that she could add a new hard drive to her computer. All she has to do is plug the drive into the wall and into the back of the computer. We don't let her plug things in though. She's a little indiscriminate about what plugs into what yet, so I would do it for her. If I had to prove the point though, I would. She could do it. I dare anyone to let their two year old install a hard drive on their DOS box.
Well, time marches on and Jordan hit three. My wife was shopping at the mall and one of the stores had some PCs set up running kid's software under Windows. One of them was running Bailey's Book House, a program Jordan has been running for a year or so. Jordan started playing with it, but couldn't get it to work. She finally slammed the mouse down and announced, "This 'puter sucks!" It's so obvious that even a child can see it. It's also a great justification for the one button mouse.
My wife, Cary, is another fine example. She was a hair stylist. Her sister gave her an old MacPlus, no box, no manuals, no hard disk. She told her to take it home and check it out. Cary was reluctant. "I can't even set it up" she told her sister. Jerry Lynn said "Nonsense! Plug this in there, this in the wall and that in there. That's all there is to it." Cary said, "Hey, that's easy" and went home. She set it all up and started running programs. It was that easy.
Cary had heard how difficult computers were to use, but Macintosh pretty much blew away that notion. We met when she took a Hypercard class I was teaching. Now she's teaching PhotoShop and QuarkXPress classes and making a lot more than she did styling hair. She's also worked in print shops and got to see first hand how lame PCs were from people who brought in their stuff to print. It was always easy to tell who was using a Macintosh since their stuff almost always looked better (after you got them to stop using every font).
Another example of simplicity is how I just added that picture to this document. I pulled my QuickTake out of the drawer, snapped a picture, plugged the camera into my computer, pushed a button and the camera appeared on my desktop just like another disk, although it looked like a camera. I then opened the picture in my image program simply by double clicking on it. Then I made it smaller and saved it in JPEG format. Finally I referenced it in this document. Later I'll copy all of this to the Macintosh server this is running on simply by dragging it to the remote disk's window. None of it gave me any grief.
A lot of Windows users are defensive about their machines, much like us Macintosh users are. After all, we spent a lot of money on these machines and we want to convince ourselves that we made the right choices, or at least that we didn't make the wrong choices. That's human nature, and it's understandable. Let me make one thing clear here, I'm not slamming people who buy or use DOS boxes. They are useful. They are cheap. They get the job done. My issue is simply how much work they are to set up, get running and keep running. I've used DOS and Windows. I've used several varieties of Unix. I've used VMS, MVS and OS 370. Now I use the MacOS, and I've never been happier. It stays out of my way and does what I want just as I expect it to. Can you say that about Windows? I don't think so.
I can't really stress this enough, and it's something you won't get until you've used a Macintosh for a while, but when you're doing something complicated and you want to do it just a bit different, you can almost always get it done simply by holding down the option key when doing whatever you normally do. The option key is commonly the function modification key, basically switching whatever the default function is. The shift key is a constraint key, normally horizontal, vertical and diagonal constraint, but it could mean any kind of constraint. It's that realization that these features will apply when you are using a new program that adds up to that "Man, I know what I'm doing" feeling. That's one of the things the Macintosh encourages, the feeling that you are in control and know what to expect. Words don't do it justice.
All I want people to do is consider the Macintosh. Apple has this phenomenal brand recognition, but people don't seem to consider buying Apple computers because they have this mistaken impression that PCs are better for them because most people "speak" PC. If it's really important to them what the majority of people are doing, they'd probably better be learning Mandarin Chinese too then. 
I've been the lone Mac guy at an all PC shop. It's not a pretty position most of the time because of the incorrect assumptions and constant justifications that you have to defend against, but it is fun when people come in and start asking questions. Then you get to show them what you can do. One of my favorite demos has always been the multiple monitors game. Macintosh works great with several monitors. The PC guys never could grasp that. "Do you have 2 machines here?" Then I would drag a window over so that it was half on each monitor. Their jaws would drop. Most of them have seen that stunt by now, and they try to tell you that they can hook several monitors up to their PC too, but they always seem to forget that they can either look at the same picture on all of them, or only have their debugger on the other one. The Macintosh has anything on any screen. It is so absurdly useful that I can't even justify it, except to say that I'll never give up my second monitor. I work on one and have reference materials and other things on the other. It's ideal.
My friends have bought Macintoshes. They have never regretted it. I have a friend in Seattle who has his machine call my machine and drops off pictures that he has scanned in simply by dropping them on an alias of my disk (the computer makes the call automatically). He's not a computer guy. He's a chemical supply salesman. It's just that doing his expense reports with his Macintosh is so easy, that he has plenty of time left over to play. That's what Macs are all about.
But the point here isn't about why my wife, my daughter, my friends and myself like our Macs. It's about what other people say about the Macintosh. I've been collecting articles which advise people about what machine to buy, and the choice is always Macintosh. If an article has recommended buying a PC, it's because they had to. That was a given before they started. If they could consider a Macintosh, they would almost always buy one. It's really that simple.
Of course, at this point people bring up the price issue. "Macs are more expensive" is the battle cry. It's simply not true. I spent $800 complete for the computer in the picture above. Mind you, it was a deal, but it was open to anyone. That's a Performa 575 with a 68040LC, 5M of RAM and a 250M drive. It has a built in microphone, stereo speakers and a double speed CD ROM drive. The monitor is a built in 14" unit which can display up to thousands of colors; that's 16 bit color to the geeks in the audience. You'll never find a better deal for a PC unless you are willing to build it yourself.
For the curious, I bought this Mac through an online auction company called OnSale. They have all kinds of stuff, although they sell out of Macs very quickly (what a surprise).