What % of those that wait regret it vs those that don't?
I have no way of knowing that. And it doesn't seem yo do either.
Why else would they regret it?
presumably because they get trapped in a boring or abusive marriage because they never had a chance to see what life could be like.
I got addicted to porn (less intense than sex). It changed my brain and I regret getting addicted. I hope others don't make the same mistakes I did.
That's not the same thing. You said that sex changes your brain, which is false. Then gave an example of being addicted to something related to, but not sex. People can become "addicted" to pretty much anything. Games, working out etc. So if you think that is a valid argument, we should ban workouts.
This would be way more common if the school system didn't tell people to never start.
my school did tell people not to smoke. It doesn't work. Teenagers want to rebel. If you tell them not to do something, they want to do it.
The point of celibacy before marriage is to increase a man's power over his wife.
This is probably not true if both people wait.
It absolutely is. It prevents you from having any experience in a relationship. So you don't know if you should leave because they are a jerk. Because, for all you know, that's how all relationships are. This leaves women stuck with abusive and controlling men.