I think if people took the courtship idea seriously it would actually dissuade them from marrying too soon.
Agreed.
As for the no sex thing are there some kids that get married quick for the sex angle? Sure, but it's not a large number.
I can't vouch for any numbers, but I do know that it can hasten a decision. I don't think kids are necessarily thinking "ooh, we should get married, then we could get down." But I think the prospect of being allowed to do what you have been forbidden to do for years can subconsciously effect focus on some of the other aspects of marriage. I'm not saying kids should be having sex first, but I think that plays into mormons having a younger average marrying age.
Kind of a catch-22 there
Exactly.