Because their work does not directly financially support the university in the short-term, so any forms of protest negatively affect their own advisors while th

Because their work does not directly financially support the university in the short-term, so any forms of protest negatively affect their own advisors while the institution feels very little impact. There are still student unions and this is an ongoing discussion in the academic community. Again, why do you claim phd students are "not assertive" with "impaired cooperation skills"? Or is that just a personal judgement on your part?