Okay, how about I explain it another way:
Lets say you have a game of Chess, with sex scenes in it, and the only way you get to see a sex scene, is to have your king taken out. The point of Chess is to checkmate the other player's king. But, if people want to see the sex, then they'd either have to fail on purpose or get defeated normally. But the point of the game of chess is to win, so, if you are intentionally failing on purpose, then the gameplay is irrelevant and ignored. That is a problem, when a developer sinks 10s to 100s of hours into crafting a fine experience of a game, for the average user to ignore it all to get at the sex. What a waste of a developer's time.
Now, if you took out those sex scenes from that game of Chess as a failure state, and instead made them available, by winning the game, you'd see people playing Chess normally, and trying to succeed. Then you wouldn't be incentivized to fail at all, but rather incentivized to play the game as the developer intended it to be played. If people are considering the gameplay elements optional, then that IS a major problem for the developer.
Or put another way: If a developer of a RTS invests their time and energy into animating units, that never get used by players, because of one reason or another, was it really worthwhile for the developer to create them? No it isn't.
A gallery, which unlocks scenes and environments, by playing the game normally, would benefit the game, as people would play the game and enjoy all the stuff the developer put a lot of time and effort in, in the manner that they had intended. Then people wouldn't fail on purpose and get to enjoy the hand-crafted experience the developer spent so much time on. By rewarding failure with sex, and having no other way to get that sex, people will fail on purpose and ignore everything the developer is working hard on to create.
I do not see how you do not see this as a problem. Maybe its because I develop and design gameplay systems all the time as my job, and therefore I understand the problem better.