> people who do PhD are not actually very assertive on their own and they have very impaired cooperation skills
Where exactly are you pulling this from? That has not been my experience, both from my research lab and from other students I've met at a variety of conferences.
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?
They do organize, PhDs at my uni (grad students in general) have their own union which negotiates contracts, benefits and minimum wages. The issue is that there's only so much they can do given their position as people more dependent on the system than the system is on them. Especially when adding in how different PhD programs and funding can be between departments or even within deparments.
Where exactly are you pulling this from? That has not been my experience, both from my research lab and from other students I've met at a variety of conferences.