* No advertisers would bite anyway. Unless you show ads for like body pillows or shady VPNs like they do on 4chan, most advertisers don't wanna platform on anything even resembling porn.There's no advertisement (neither does he advertise nor does he accept advertisers), no merch, he doesn't commercialize his streams, he doesn't release updates as much as he should to gain attention (sadly), he doesn't sell the game on steam, he doesn't really charge people for early access - he indeed doesn't make people pay for the game at all.
Microtransaction would surely be predatory, but as said, I'm sure many actual companies/devs would try to add premium content into the game, if they had such a huge audience, that's obviously willing to pay.
* No merch producers would bite either (and, let's face it, it's not like STS has super-iconic character design to warrant it either)
* Aren't his exclusive streams for his Patreons anyway?
* Steam wouldn't tolerate this game because they don't allow porn games in a high-school setting. Even if the characters are 18+.
Charging for EA is about the only thing he still could do.