Part of the problem is that the topic is so radioactive, that coming forward with a story of abuse, and the legal/media circus that follows, really puts the abuse center stage in people's view of you. Most people absolutely do not want their most defining attribute to be "person whose family member raped them", even if it comes with extreme sympathy and understanding.

For many, probably most victims, they just want to forget about it and let it vanish into the past, and ideally someone else who was abused by that person comes out and has them jailed.