Why use old computers and operating systems?

On this blog, I write about the various computers I use and about the operating systems I use on them. Apart from Windows 7, which is relatively modern, these include Mac OS 10.6 Snow Leopard, which at this point is quite old, and Mac OS 9, which is practically ancient. I'd like to talk a bit about why I use such old systems.

A good, succinct answer to the posed question. I love using older systems not for nostalgia's sake, but simply to learn, to experience systems I didn't get to experience when they were current because I was too young or the hardware was too expensive. A few posts down I mentioned I'm about to buy an old HP-UX workstation, and I can't wait to get my hands dirty and learn as much as I can about it.