Not because the would-be molestor told them so, but because the child knows *from experience* that bad/scary things happen when mom or dad gets told things they don't want to hear.

Too often, that's the same parent who will ask, years later, "Why didn't you say anything?" They honestly don't remember that the kid did say something and got punished for it.

If it's not too personal, was your mother clueless or nuts? My own was both, by turns; she had her clueless moments, but the fundamental problem was that she didn't really understand that events had causes.