I don't think it's crazy to not want chidren, i don't have any and i don't intend to have any.
People do look at you funny though when you're passed a certain age and still haven't settled down with a wife and kids.
You become an oddity, something awkward, all my former friends from school have settled down in their early 30s and that has left me as the weird guy who remained single and is better avoided.