Sensible people just use whatever does the job best...
I'm typing this on a macbook (a black one which is a couple of years old). It is running Leopard. It has a virtualised Windows XP installation running happily under Parallels. I'm using it to connect (using the PC version of Citrix client because it's better) to my office as I sit here at home doing work. At the office I have two XP boxes, which are used for everything from documentation to software development in various languages. The database servers at work are running Oracle on some flavour of Linux. All of this is perfectly simple to deal with. I used to use a WinXP laptop (which was 5 years old when I retired it) and the major reason for moving to a mac was that at the time Vista had just arrived and I just didn't want to waste large chunks of my precious time dealing with the sort of hideous messes which were being reported with Vista. Life is just too short.
Since moving to a mac I've found that it really is (in my opinion anyway) a slicker system to use, with very few of the annoyances that Windows inflicts. But I can get work done with either, just as in previous stages of my life I've got work done on everything from CP/M machines, through various flavours of DOS, Windows from 3.0 onwards, real computers running flavours of Unix, PDP-11s running all sorts of weird OSs, VAXen running VMS, etc etc. At the moment the setup I described above gives me the most flexible, irritation-free computing environment which fits my needs, and for that reason I'm perfectly happy that I spent something like £1300 on the macbook a couple of years ago instead of going for a cheaper PC laptop.
As for people who build their own PCs... In my youth I used to get involved in a bit of car maintenance - I know how to adjust the valve clearances on a BMW small six engine, or adjust the idle speed on a stromberg carburettor. Now? Life is just too short - I take the car to the garage and get someone to service it and pay them some money in exchange for doing so, because I am no longer interested in the nuts and bolts - I just want a machine with 4 wheels which gets me where I want to go with a minimum of fuss. It's the same with computers.
People need to get over their prejudices and just use what they find most comfortable. If that involves spending a bit more money to get a better experience then it's down to personal choice.