Well, for one, I got the system for free, and I don't have the funds to invest in a new Mac Pro, or even a new computer at all. Plus, all the OS X applications I use are universal binaries, so support for Snow Leopard and Beyond is a non-issue as of now. I'm also perfectly fine using the last PowerPC-supported binary if support for the architecture is dropped. To be honest, I'm not picky about my computers, so long as they run what I need/want them to and do it well, and the Power Mac G5 suits my needs and then some.