It's no conspiracy. The casting couch is the worst kept secret in Hollywood.
I'b bet the overwhelming majority of actresses who started out young (as they all did) at one point early in their career had sex for a role.
I think the parents were so star-struck, they turned a blind eye to it. Some Hollywood mom (who lost her own virginity at 16 to a high school loser at a keg party) thinks, "What's the big deal? At least we'll be rich and she'll be famous!"
And today the girls won't talk about it because partly of shame but mostly because they know they'll never work again. They'll be blacklisted. And every one of those former kid actors, now forgotten, dreams of the big "comeback" role that puts them back on the map.
'Sunset Boulevard' (1950)
The sick truth is that the parents often pushed for it.