That's how it went for you, right? Your first time?
Look, no one has ever said "This Tom Hanks movie will teach me how to have sex!" But the reality is that by puberty, 99.99 percent of the sexual encounters a teenager has seen will have been in a movie or TV show, unless they grew up in a super open-minded household. And what they get, over and over, are scenes like that -- a jump cut with no actual nudity, no foreplay, no one procuring a prophylactic unless it's for a joke, and the guy (in this case, one with no experience) bringing the woman to borderline transcendental ecstasy with little effort.
Think of how differently this scene would play if there was actual realistic foreplay -- Leo with his hands or head between her legs (that is, the thing that has to occur first for most women to have any chance of orgasm). To audiences, that suddenly seems far more explicit and graphic ... even though to anyone who's had sex, it's the bare, routine minimum.
In a world in which American sex ed is barely allowed to mention pleasure at all, the "lessons" we get are demonstrations of sex that in reality would leave a confused guy saying, "You didn't finish? But I was thrusting and everything! I was just about to say it was the best date ever."