When it comes to masturbation, how can it be a waste of seed if, without masturbation, the seeds come out anyway? (Remember "wet dreams"?) And girls! They ovulate once a month (normally). If they don't get pregnant, is that a waste of an egg?
As for little girls pleasing their dads, as has been shown by the Polynesians (and others), child/adult sexual encounters are neither helpful nor hinderful. It's just good sexual feelings to be enjoyed while you can. Little girls like it, little boys like it as do people sharing it with them.
Modern society is so fucked up regarding sex that it is probably impossible to unfuck it. I'm not even going to try.