OS nostalgia is stupid but application nostalgia makes sense. If you happen to have applications for IRIX that would be expensive or impossible to replace, then keeping IRIX on life support is reasonable. For example I happen to have a licensed copy of PTC Pro/ENGINEER for IRIX/MIPS. There's no other way to use it. This is the same reason I keep Win2k virtual machines hanging around. That is the only way I can still run my copy of AutoCAD R12.