This is literally addressed in the FAQ. (not directly, in these words, but still.)
buuut that's a cop-out response, so I guess I'll add my two cents on the subject.
I think that the existence of limitations is an intrinsic part of "the aesthetic" of chip music. That being said, I don't think that what those limitations actually are is all that important. If that distinction makes any sense?
So it's less about using any particular set of limitations—number of channels, kinds of sounds being used, hardware—and more about coming up with some constraints, and sticking with them. Using "vintage" hardware just happens to be a straightforward way of setting "hard" limits (ha), in a communally-consistent way.
The rest is extra credit.