They didn't want to destroy their careers by calling the police on powerful industry figures or have to face someone with very expensive lawyers? Very likely if it happened to a young person some time ago when they were just starting out in their career. Plus a lot of sexual assaults don't get reported at the time for psychological reasons, especially if it's not rape. Since a couple of people started talking publicly it's now turned into a movement exposing what may be an ingrained dodgy culture in the entertainment industry.
Re Spacey, I can't decide if he's purely attempting using his sexuality as a defence, or if he's decided it's pointless trying to stay in the closet now.