It's because the writing has been put on railroad to get the story to all the sexual situations they came up with and decided to throw into the game.
In their rush they never properly considered how to write the scenarios where a player disagrees in a consistent and organic way. It is just assumed that everyone are always going to choose to enthusiastically agree. It leads to these really problematic and toxic situations where companions don't respect the player's consent, assume consent (hello rape culture, so happy that you made an appearance here) and act in a really inconsiderate manner around what someone is comfortable with in sexual situations.
