Why do films include male nudity?

If you're watching movies to see naked women why don't you watch the ones where showing naked women is the whole point of the movie?

I for one watch movies because of the genre and the storyline and I've always found it ridiculous when a movie avoids nudity at all cost just to keep the age restriction low, but wants to have spicy scenes in it anyway.
When there's a sex scene in a movie and the actors/actresses keep their underwear on and/or make sure the blanket covers everything all the time, before, during and after the act, that's just unrealistic nonsense and that's true for male as well as female characters.
Same thing when after the act one of them gets out of the bed and the camera angle is carefully chosen so it will show them only from behind even when they speak, that's just not natural behavior.
I'm always cracking up when a movie shows a woman in a bathtub where either the camera angle is kept so low that one can only see the head sticking out, or the bathtub has more foam than water in it, because I know for a fact that the actress isn't naked in there, she's wearing skin colored underwear underneath all the foam, so not even the film team gets to see her nude.

In old times the camera wouldn't follow characters into the bedroom, it just showed them entering the bedroom, closing the door and the camera remained outside, topic solved, nothing unnatural there.
Then in the 70s or so producers went for nudity all over the place, having nudity it almost every movie, even when not expected by the viewers nor required for the story, over the top exaggerated to a point where that didn't look natural anymore either.
Quite a lot of movie stars became famous after they were shown nude in a movie.

Nowadays it's the combination of age restriction, actors and actresses not willing to be shown nude on camera and producers who want to show scenes as spicy as it can get without increasing the age limit while keeping the limits the contracts with the actors/actresses have, that gives an absurd outcome of what a movie shows and doesn't show.
Specifically absurd it gets when they do show nudity during spicy scenes but carefully avoid touching any sensitive parts of each others bodies, exaggerated to a point where it becomes obvious that even the actors/actresses realize how unnatural it must look to the viewers.

To get to the question you raised here, it would be even more absurd if female characters were shown nude in a frontal view but male characters weren't, to my mind that would be even more unnatural than avoiding all nudity during spicy scenes.