Thanks for this post. As a European I wasn't aware these rules actually existed. I thought they were merely "Hollywood" tropes to have explicit romantic interest in fiction while keeping a G rating.
A lot of it might have started that way —French kissing for instance has a complicated and not well documented history of misunderstood euphemisms– but they have influenced culture and expectations. Most people have lived through less relationships and break-ups in real life than they’ve seen in movies.