Grad students are both apprentices and employees. Typically the university charges tuition which is waived if they TA (teaching assistant) or their research advisor (or department) funds them out of their grant or operating budget. I don't know for sure if this is the reason but it is a sleight of hand to either get more grant money into the operating budget. Grants typically allow some percentage overhead, I don't know if research associates are included in that or separate chargeable "line items".

Anyway it is like this all across academia except for the "exceptional" students who are recruited. They tend to get everything paid for.

UCLA, UCSC, all of them pay poverty wages. Grad students have started unionizing though to get better conditions. In reality grad school in the US is basically an immigration pipeline. We should import the best and brightest. The New York times says 80% of US grad students are foreign [1]. This is the reverse of 80% of all US college students being US citizens.

That's absolutely crazy to think about. Why aren't more US citizens going to grad school?

Either they are not qualified, which means we are not educating our college students to a sufficient standard, the poverty wages are so detrimental that only foreigners will put up with it. Something is clearly broken.

1. https://www.nytimes.com/2017/11/03/education/edlife/american...