I’ll take a stab at it. It’s because you are not dating you are trying to find a long term partner. You know in your mind how that person looks and acts. Within in a few minutes you have unconsciously made a decision. Because you don’t want to hurt anyone and you don’t want to sleep around you end it after the first date.
I’m the same way minus the sleeping around lol. When I OLD and I don’t see the potential finish line I typically end for the woman’s sake. Though in real face to face interactions I’ll do hookups because I feel there are no expectations unless stated before hand.