The fuck you mean “how did this happen?”
Steam didn’t allow adult games then they did. So now there’s adult games.
Sex sells… News at 11
valve didn’t want adult games on their platform, shortly afterwards gog has adult game sale, valve goes back on their stance and allows adult games from then on forward (that get past their approval process, non-adult games still get denied. rip dungeon travelers 2).
As long as there’s an age restriction and tools to filter out anything you don’t want to see (which there are), why is it a problem? Most people on steam are adults. Just hide it if you don’t want to see sexual content.
There were porn games on the Atari 2600 (Custer’s Revenge, Beat 'Em & Eat 'Em, etc). Porn is ubiquitous to humanity. Always has been and probably aways will be until we evolve past sexual procreation.