I think drawing in black and white certainly does restrict the ways you can depict the subtleties of skin tone, and it's hard to draw people in a traditional thin lined ink drawing without having them look pale eg as in this picture I found on google.

That said it's not inevitable that black ink + white paper = pale figures, see for example this post on the way russian cartoons use black as the default.

I'm not sure about changing the background colour, I can se that being a useful technique sometimes especially if you just want to do a simple line drawing but..hmm. *ponders*