They don't think they will be believed. They are afraid for their families or themselves. And the main reason children do not disclose is because they feel dirty. It is important that we talk to the child, but be careful not to make the child fearful. For instance, California has 40,000 registered sex offenders and only part of California database of sex offenders are online.
Some states show their pictures, but it varies depending on the state.
We do believe that the majority of sex offenders were abused themselves as children. Here in the UK, you have no access to child abuser records. How do we protect in any other way which is related. Well, my first suggestion for the UK is to find someway to pass legislation to make sex offender databases open to the public. Next, parents should be informed about this subject and inform their children.