Experts (and I assume this refers to criminologists and therapists) view it as a means for establishing control. THat in the mind of the rapist sex is inherently about the desire to dominate women, even punish them.
May explain why someone like Weinstein chooses to do all this stuff to women instead of paying for it, which he could easily do. Paying for it is a form of control but one where the woman is willing to accept it. Paying for it also implies that one has to and therefore creates a limit to one's power over women. Coercion reflects his position of power and his ability to control women.
Pure speculation of course. Maybe he is just a sick ******* who enjoys making women do things they dont want to.