The vast majority of users don't want Linux on the desktop because it get them nothing they find useful. That's pretty close to dead in my opinion.
The common user don't understand how to use it. They won't understand the difference between Linux and a Linux distro. They don't have anybody to hand hold them through their tasks, and most of their software won't run on it without arcane bash incantations. Plus the community in general treats them like idiots.
But that's not even the real problem. What makes it dead in my eyes is actually people like myself.
I've ran Gentoo, YDL, Slackware, Debian, Ubuntu, amongst other smaller distros. I used to be a fan. Now I'm completely indifferent. I simply just don't care enough to pick Linux.
Why? Because as far as it has come, Linux holds itself back. No stable ABI's? Come on, every other OS can upgrade kernels without recompiling every driver. KDE/GNOME/Unity/etc infighting and all that is ugly to watch. The last straw was Ubuntu software updates on a dev machine years ago. Bog standard Dell Precision 370. Pentium4. Intel board. No extra accessories. It's the stereotypical P4 box.
I clicked update on Ubuntu and Ubuntu made itself unbootable. (This wasn't a major update either, it was simply the typical package updates from the repos.) After fixing it manually, it did it again a month later. Then I transferred all my work to a Mac and that was that.
Since then, all my machines run OSX, OpenSolaris/OpenIndiana, WinXP, or FreeBSD. (in that priority)
Shit just works... and more importantly, stays working.
If somebody told me that Linux has fixed all that in the past 4 years, that'd be nice. But it wouldn't convince me to go back and try it again.
I feel I'd gain nothing from using Linux.
As for the people who buy a Mac to run Linux because the hardware is better supported, it's just a matter of time before they switch to OSX.