you have three variables, titty-streamers and their audiences, ad revenue/sponsorship, and gameplay streamers.

if twitch does nothing they keep the viewership from titties. they don't have to admit to sponsors they market sexuality. and ok.. they piss of some gameplay streamers (who they have the most leverage over, anyway).

if they stop it, they lose titty audience.. which drops viewership.. which drops ad revenue. OR, they admit to selling 17+ content.. which loses them ad revenue and sponsorship.. and hurts their parent company reputation. and their reward? gameplay streamers are happy. -- ... so? that's not much of a reward.

this is why they do nothing. please stop acting like their behavior is nonsensical, it's completely logical short term. but it is non-sustainable, and it's getting closer to that point of breaking.