One only has to remember what things were like with Linux 10 years ago, in the year 2000, to know why the interest just isn't as strong today.
At the time, it had a massive advantage over the Windows 98 platform, which was the common desktop at the time -- it crashed constantly and required formatting every few months, and was vulnerable to total crap like TCP/IP flooding, running unlimitedly powerful
Linux, on the other hand was rock solid. It didn't crash, it had anything you needed readily available and installable. Need a web server, an IDE, a hex editor, an image editor more advanced than mspaint, PERL, an audio player, an IRC client or anything else? It was there, no running keygens or installing adware. Same with using existing things like ICQ, IRC, the web, usenet, etc. And they were actually competitive in terms of friendliness compared to what was on the Windows platform. You could also script them no problem from a totally OP command line.
But it was a terrible pain to install for a young amateur compared to just popping a LiveCD today. Have fun partitioning your HD with raw fdisk (cfdisk if lucky) and setting up XFree86 by hand to see any graphics. Try setting up non-PNP ISA devices with screwy drivers -- often you had to go hardware swapping for something specific, like a $10 Crystal Sound card. Try rebuilding the Kernel with an ALSA patch to get that to run. Try not using a packaging system for anything -- RPM was terrible at the time, you were better off just compiling things.
But socially, if you could pull it off, you were pretty elite. You had a solid, invulnerable, insanely powerful OS with every tool you'd want at your hands. It was rebellious against the suits and it had the promise of an open source world. The programming was much better -- OpenGL was way, way easier to write for than DirectX 6, which was just nasty, and was cross-platform to boot. The internet population was far more technical at the time and also respected it. Social networking / multimedia was years away from being mainstream at the time. Anyone who ran Linux wasn't a 'n00b' or a 'lamer' on primitive web forums, Usenet, IRC, etc.
Today? Windows XP/Vista/7 has been comparatively stable and isn't nearly as vulnerable, unless you're just stupid. There's mountains of OSS software out there for every task that runs under Windows, if it wasn't built to run under Windows. No one cares that you run Linux, and will just get frustrated if you can't run the 10% of things a PC can. Ten years ago, the biggest PC game -- Quake 3 -- ran great under Linux, but try getting MWF2 to run under it today.
So there's no real motivation to get into it now -- it doesn't have the appeal comparatively it did 10 years ago.