The $6K you refer to is a different matter. Some institutions do...

The $6K you refer to is a different matter. Some institutions do that (sometimes $10K) to provide an incentive for new PhD recruits, and most don't given so much funding cuts from the government (behind the scene, that money also comes off your supervisor's research funds). In engineering, APA (a living allowance, and not research money) is almost guaranteed to all our domestic students, and has been so for a long time, which is a good thing. Most first and second tier universities do not let academics hire PhD students without proper prior funding in place (either student have APA or academic staff have enough fund to funnel through a university scholarship to be paid to the student). Things are different in different fields. And also you mentioned some can only support themselves by working for their advisor (rare in engineering) but that money also indirectly comes from a government-funded grant.