Very often in dysfunctional families, the children will "parent" the parents, in that the child is forced to behave with more maturity at a far earlier age than is typical. There was a story here in Dallas of an 11 year old who was driving his drunk father home from the bar. I remember feeling, not superior, but that I was more intelligent than my parents and I used that to build a fragile confidence and find a way out of the hell I grew up in.
There are all sorts of reasons victims don't tell. Mine was that I got tired of telling and no help coming. I remember telling a woman who came into my father's store (I was 4) that "My daddy hurt me in my bottom." To my way of thinking, I had told everything. I remember the look on her face when she realized what I had said. I remember another time telling my grandmother and she slapped me and told me to never say that again. She told my mother and, after Nanny left, she hit me till my nose was broken. After a while, you just give up and keep quiet.