When these social networks became connected to ones professional career.
Let's say you are a marketing director for (small video game company) and are using social media (Twitter, Reddit, etc. etc.) to market, network and hype your games.
Suddenly, porn appears. Possibly your characters in the game get rule34'd. Do you engage?
No one is going to sacrifice their 30+ year career for a bit of free advertising to a video game that you're only going to put 1 or 2 years more into.
I think "mainstream" porn is accepted for the most part. But you don't have to go very far before people ask "How old is that character by the way?" and then everything goes to shit.
Are children following your professional account for video game news? Etc. etc. Its just too much of a risk in practice.
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EDIT: Wow, a bunch of downvotes. Okay, I'm a Pokemon fan. Tell me, how long do I have to go on Twitter before I accidentally come across rule34 of Pokemon characters? We all know what's out there, I'm sure we've all seen the internet. Nothing against rule34 artists or anything, but these are not things you want to interact with if you're making a career out of video game marketing. There's some pretty uncomfortable taboos that are being explored here.
Incidentally, that is also the case on Bluesky and one reason I would not dare to invite anybody on there until they address it.