I don't know what you've been watching, but from what I've seen, most H-anime goes
way beyond just "hot making out scene."
Aside from regulation, I think it's because watching people make out is not very interesting by itself. Basically making out is the same as foreplay, except the former doesn't immediately lead to sex. So, I'd rather watch the whole thing instead of stopping in the middle, and I assume this is true for most people as well.
Furthermore, make out scenes are not very good plot devices, either. A simple kiss or (implied) sex is enough to establish the context and invoke an emotional response from the audience. Again, it is at the awkward middle where it either takes too much screen time (compared to a kiss) or doesn't pack as much a punch (compared to sex scenes).
I believe this is pretty much true for all forms of fiction, not just anime. The one exception I can think of would be teen movies. Since the pattern there is ones first sexual experience, a make out scene definitely would fit somewhere along the story. Come to think of it, is there an anime that follows the teen movie template?
Anyway, the closest thing I recall to a "hot making out scene" is in KareKano. What you see is Anima & Yukino passionately making out, but it's pretty clear that they're really having sex; Gainax just can't show it.
