I think it has to do with the fact that these weren't things the average family had, so there isn't the childhood-nostalgia factor involved (for most.) Even over on Nekochan, most of the users are either industry old hands who used them at work or people who read about SGI boxen in the press back when computer graphics in movies were a hot new thing.
Anyway, I've owned a couple Sun Ultra and Ultra II workstations in the past, but I had to give them away to a good home when I moved. Since then, I've picked up a nicely-loaded Blade 2000 (2x1GHz UltraSPARC-III w/8GB RAM,) but I've been having a devil of a time getting it working (the video card's an XVR-1000, which apparently can only be used as a framebuffer console with the 13W3 port and not the DVI or VGA ports, so I can't figure out if my complete inability to get it to come up with a framebuffer console is down to an issue with the card, a dodgy 13W3-to-VGA adapter, or who knows what. On top of that, the hard drives I picked up were low-level formatted with the wrong sector size and I'm having a hell of a time figuring out how to re-format them to what Solaris expects when Solaris won't map them because they're the wrong sector size...oy.) I've also got an SGI O2 that I really need to use more.
And yeah, "not many games" is probably also a factor - though it depends on your requirements. I'm generally pretty happy with Quake, some emulators, and a decent selection of roguelikes, so that's not necessarily a barrier.