I beg to differ, ElevatorVibes, since Steam does support NSFW content now as I have seen on the FREE Game "Blood and Lust" which included a NSFW Scene on the path I was playing through it.
Also you can now chose in the Preferences in Steam whether or not you want to include Games, that Show Adult Erotic/Sexual Content or not.
So, I think this should be no problem, unless other requirements prevent Game Developers from uploading their Games there (would be interesting to know which ones that might be then?).
Cheers and enjoy the cool Games on here and Steam.