I read all what you said. Still think it's very unfitting and more an excuse for people to jack off.
I call it more as something sick and useless, rather than mature. If it actually adds to the other atmosphere and tone of the game that's otherwise there, like in FO3, then I can accept something erotic. I certainly don't see it adding to that in Skyrim.
What makes it fit FO3 but not Skyrim? I honestly don't see why it would fit one and not the other. I agree that FO3 had more of an advlt atmosphere than Oblivion, and that type of thing does add to said atmosphere, but what I (and I believe the OP) was trying to get at is that Oblivion
should have had a more advlt atmosphere than it did, and things like this could add to that atmosphere if correctly implemented. Morrowind most certainly did, as did Daggerfall. You can disagree, but I felt that Oblivion had a much less advlt tone and atmosphere than the previous TES games, largely due to the lack of any sort of underground, morally ambiguous or questionable people/places/things like drugs and six.
I certainly don't think that this should be any sort of large focus in the game, but just the simple presence of something can add a lot of tone to the game world.
P.S. I don't believe the actual prostitution guild even existed in Skyrim in the first place, and I don't think it should be an actual, join-able guild; I just want more of these seedy, underground type places, people, and groups in the game because I personally believe they make the world much more interesting, mature, and realistic. I also missed the presence of join-able religious factions like the Tribunal Temple and the Imperial Cult in Morrowind. I believe there were some quests for the Temple of the Nine, but they were very unremarkable, and it wasn't a faction like those in Morrowind.
I think that, for black and white to really stand out, there need to be various shades of gray in between them. I want the choice to be good to actually include decisions that require me to miss out on certain aspects of the world, or choose to allow myself a little gray-area. I want the choice to be bad to have an actual impact on how the world see's me, and how I see it. Oblivion lacked this severely, and I would like for more moral ambiguity in Skyrim in many different varieties.