Earlier quoted context omitted.
Do you believe a Phd student should risk questioning his supervisor? Which could likely end a planned career in science right there?
That's a better point, but the student still couldn't be expelled, which is the workplace equivalent.
Some people have tenure, but some people win lotteries too.
The hiring process appears objective, what have you published and so on, but in reality it's set up for the bosses to game. When there's a letter to Nature, for example, it's very much up to the boss as to which student gets to be first author.