In my part of the world (central Europe), the vast majority of PhD-students is actually employed by the university they aim to obtain the PhD from. So in addition to working on your thesis you most likely have to support other research projects as well as do a lot of teaching. The model of a free PhD student certainly exists, but it is rare.

It's pretty common in ivy-leave US universities (which is what the article is biased towards). There, you only have to TA a bit and you certainly don't work for the uni or the dept.