I disagree with your thesis entirely. I had plenty of variety between 16-26. I think it's because of that variety (and I'm not saying I was Wilt Chamberlain) that I was able to recognize what was truly special. I have to imagine that if I'd married young(er) and retained my virginity up to that point, I'd be climbing the walls right about now wondering what else is out there and is that something else better than my wife?
It makes sense. Self-mastery is neither easy nor automatic. It's a learned thing, learned from experience. A person who transitions easily into sexual behavior before marriage isn't training himself in the impulse control that he or she will need after marriage, when impulse and opportunity ---with someone other than your wedded spouse--- can grab you and pull hard.