I think they get paid very little, plus they do alot of hard work (well I think it is, going back and froth, remembering who had what, even having to stand for ppls nakhray etc esp w/ desi customers). There was one restaurant right in the heart of little pakistan, every time i went there was a new waitress (some HS girl) there, and we used to go every month or so... so that showed the employee turnover. last i checked that restaurant went out of business.
So yeah tipping is a must unless most of the "nicer" places alread include a service/gratuitiy tax in the bill.
Well then they should look for another job which offers a better wage.