I think alot of people are like me. I wanted a Mac since I began using PC's in the 80's, but always had access to a PC and did not have any reason to buy a new comp. I always got one for free from work, upgraded, or whatever. In 1997 I bought a VAIO laptop but wanted a Mac then but could not see paying the diff. Mine was only $1400 for a then fully loaded laptop. When OS X came out I really became intrested in Mac but once again did not need a new comp. 6 months ago I bought a fully loaded Tower PC for really cheap to use for games and a server. Mac Towers were to much. A month ago I needed a new laptop and got to looking and just happened to go to Apple.com and the price was right. My dream of owning a Mac had come true.
Most people just do not know that Apple is an option. Best Buy, Wal-mart, and most other stores do not carry them. The power users are not going to switch any time soon. Most of them just got done switching to the PC not too many years ago.
At this point the average user is comfy with what they have and there is no real reason to upgrade or have to learn a new computer. It is the average person that makes the money for these companies, and the average person sees no reason to switch from what they have and know, not to mention the software that will not run on the other machine.