Go find an actual market share graph for each OS to see a little perspective. OS X is at 8-9% after all these years of heavy marketing.

I think there are SEVERAL reasons why, that are not said.
1) People are keeping their devices longer
a) PC’s are more and more reliable
b) hardware wise, there is no need for a new machine. several year old machines work FINE for most people.
2) Upgrades. Most PC users I have noticed will add more memory, more storage. Apple users? I have noticed don’t care and mostly end up buying a new device if those are needed.
3) The apple “experience”. Apple is heavily on the newest device. Ironically, it’s the apple users who are replacing their devices on a more frequent cycle and the non-apple users.
4) Apple users have the $$$. economy wise, well people are keeping their devices longer. those who have the money tend to throw it out more often.

What I have found interesting is
about 80% of the apple users (well more like 90%) have spent HUNDREDS on Microsoft software.
About 50 to 75% are running some sort flavor of WINDOWS on their machines
The long time Mac users (note: not the fanbois) are looking at replacing their Macs with windows powered machines.

This sounds really weird, but it seems that people prefer having Windows over OS X. They just think it’s a better OS. What happens is that there is this “notion” that Windows = sucks, fat, ugly, old; while OS X = hip, cool, popular, fast, etc…

The only people who really HATE windows are the people who simply DO NOT even touch it. They refuse to touch it. But, Windows users? I have known countless who have used OS X and have tried to like OS X for years, and for some reason it’s nowhere near as good as Windows.

I bought a Mac several years ago, to try it. Great machine, great OS, but 95% of the time, I’m running windows. And my next machine to replace it will be a Windows machine.

Of course, it’s better than a PC. your POS PC, have having used and owned a huge verity, if you get a “high quality” PC, A Mac simply cannot touch it. And when I know creative proffesionals who are going to the windows world because a PC is (now) better in the creative field than a OS X machine, that is telling you something.

I guess since Macs are PCs with MacOS preinstalled, but still, seems like a strange comparison to me. What about people who run Linux ? And what counts as a “PC sale” ? A CPU sale ? a Motherboard ? A windows Licence ?
I’m virtually still running on the same PC I did 10 yeas ago, except I’ve upgraded it a few times to get to my current rig (I5 3750K, HD7950), and I think Mac users tend to buy a new computer instead of upgrading their Macs over the years, so does it count as more Mac Sales ?

That said I don’t see the trend stopping anytime soon, even with the release of Windows 8. MacBooks are easily the best pieces of hardware on the market (though I have high hopes for Vizio, Asus, and Samsung) and OS X is significantly more conducive to the productivity of a developer or designer compared to Windows or even many flavors of Linux. Also, if you absolutely need to run WIndows, you can always Boot Camp into it on your Mac whereas setting up a Hackintosh is quite a bit of a headache (and I assume illegal) on a Windows/Linux machine.

On an aside, I hate how people have distinguished between PC and Mac, though I do acknowledge this split may have been due to Apple’s marketing. PC stands for personal computer…is a Mac not a personal computer? I try my best to say “Windows” vs “Mac” computer as to me both are PCs (they even have the same internals/processors/chipsets now) but made by different manufacturers and sporting different operating systems. The device is otherwise the same thing.