Sure, you could make an argument that this would be more realistic. But it just wouldn't work out in the game, from a practical standpoint. It would basically lock you out of most other quests until the Paul blackmail arc was completed. And that would be a huge problem, if completing his blackmail arc was tied to other events in the story, such as Lisa graduating, or Jace's party, or whatever, since triggering those events would likely require you to complete other quests.
As far as changing other sexual activities, that would require multiple versions of multiple scenes, depending on whether or not you were still playing through Paul's blackmail arc. This would be a huge increase in the amount of work PaleGrass would have to do, in order to complete a new update.
So this is a case where increasing the realism of the story has to give way to more practical realities of game development.