I disagree with "just wastes your time as you hurry to get to the good stuff". Ideally, I like adult games to have some gameplay. IMHO story is not that important, but some kind of 'fun' gameplay that you do in order to get to the 'good stuff', is. Heck, even some form of grinding can be fun. I like to unlock things in games like these, gives you something to do and makes it feel like a reward for your work. It's also an easy way for a game to have more (re)play value. Or the game could be some sort of 'sex sim', and that would be enough for the gameplay (with unlockables haha).
For terrible games that just have decent or good sex content, an "unlock all" code is the way to go. But for games that are kind of fun to play, having everything unlocked from the start is like playing that brand new game you've been looking forward to with all the cheats enabled.