It's the only os that mame runs on that anyone cares about.

No joke though, it is. If you are running Linux then odds are you are running a very basic setup with very cheap/old hardware (the only logical reason I can think of for using Linux is you are too cheap to buy windows). If that is the case you are only going to expect "the classics" to run anyway and even if you don't you probably are going to stick with the hardware you have because, again, it's a cheapness issue.
If you are running a Mac then either the aforementioned Linux scenario applies (someone gave you an old mac and that's all you have to work with) or you actually pay cash money for new Macs, which means money is no object and you'll simply upgrade the hardware if anything you want doesn't run.
The only people that are in the "I don't know how powerful a pc to buy or if it's worth it to upgrade my current machine" would be windows users I'm guessing.