As noted, most PhD students don't pay out of pocket. What this is meant to correct, as noted elsewhere, is that PhD students still have to be enrolled in class

As noted, most PhD students don't pay out of pocket. What this is meant to correct, as noted elsewhere, is that PhD students still have to be enrolled in classes while working on their dissertation, at least to some extent - and class enrollment means tuition. Full time student status is important for many, many things like health insurance and student loans. These waivers are an acknowledgement that those classes aren't actually using space, instructor time, etc. so it would be silly to charge them tuition for it. What's being proposed is essentially charging students for a book keeping adjustment. Hilariously, I think it will be harder for the top privates. Many states have clauses to prevent tuition being spent using state money so that the state doesn't end up effectively paying itself, which may still work even if waivers themselves go away. The privates would have to figure out how to define full enrollment but not paying tuition (and for some portion of a PhD students should be paying tuition, via some mechanism). And that can get tricky...