lol you are making my point, not yours. All of those 30, 40, 50 hour+ games could have the sex scenes entirely cut out, or slightly retooled so that any important 'character moments' in those scenes still happen just in a different context, or just turned into a fade to black - with zero loss in the overall structural integrity of the story. Because, just like you said, the point of these kinds of games is not the sex.
I'm not trying to be an 'intellectual' or a 'true fan' or whatever garbage here, I'm just making the (what I feel to be pretty self-evident) statement that a game like Fate/Stay Night or Muv Luv sell sex, sure, but they don't sell sex in remotely the same way as a game like... *checks front page* ... "Goblin Burrow".