When I go out on a picnic, it's not the walk, or the blanket or the view; But, the opening of the basket to see what she packed...what is the fare to be? Don't we seek what is on offer? How often have you had a deliberate review of the "bill of fare" before penetrating the basket?A playful interlude of oral exploration, also verbal, can heighten and expand the possibilities. Some rough contact and bondage is far more stimulating, but, the climax of any date is coming home, entering the doorway, the threshold embrace and the long kiss goodnight. 
All that said; there is nothing more over rated than the epidermal felicity of two unfeathered bi-peds locked in furious congress-just sayin'

I was playing a theater of the oppressed game. (Or acting in a theater of the oppressed play?)

It came from this one girl in the group who recently broke up with her boyfriend of 7 years. When you date someone for 7 years there's probably a lot of reasons why you break up, but she gave us this one story.

They'd just had sex and I don't think she got off but he did and so it ended. And she was like, "what gives?" And he's all like, "I'm done."

She confronts him and tells him she thinks it's sexist that he is of the opinion that sex is all about his big finish. (Which isn't necessarily about penetration, though more often than not, is processed through the act of penetration).

He turns it on her and says she's being racist. (He's latino of sorts). I think the historical stereotype of machismo is called to testify. She tells him to "get the fuck out" and then they break up in one of those ways that has very little closure.

So basically in the game we act out this scene in front of her and then send it through various iterations and she watches, the idea being she needs some separation to identify objectively and spatially. What I think she took away from the scene played out in front of her and in memory is that both he and her abstracted to social norms (ie. sexism / racism) when what they were really confronting were issues of intimacy and devotion. Her desires were for there to be something more than sex during sex and he was plainly in it for the sex sex.

Now. This was all sort of off topic, I just thought it was interesting demonstration of how sex can be abstracted and explored and memorialized.

But to the topic at hand. Do men eroticize penetration? Probably. I mean physiologically it feels great. And like yeah, we were built as puzzle pieces for a reason.

But is your question more, why is penetration sex? Why is what's erotic only penetration? I don't know. I can't speak for all men but I think what's erotic about sex is making someone else feel pleasure and the reciprocal nature of that.

I think eroticizing body image is more of a cultural problem than penetration.

Solveig,
Thank you for starting this insightful 'penetrating' dialogue.

 'Penetration' is not a word I think I've ever used in the bedroom.  Erotic? - Yes,

but perhaps a bit too forceful for use in most conversations when a euphemism would do.

 ie:  commonly used - I slept with her last night.
rarely used - I penetrated her last night.

It reminds me of a song lyric:
  "Mama told me not to look into the eyes of the sun,
but mama that's where the fun is.