Also, I want to add that for most people, puberty isn't over until the early 20s. It would be pretty unheard of for someone to be halfway through at 13.
Of course, that really likely doesn't have much to do with pleasure from masturbating. More often, the issue you're having with that is that it just tends to take people time -- we never really stop learning, honestly -- to learn what we like.
Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has. - Margaret Mead