Yup. And the only reason advertisers would care is if it would hurt their standing with the general public. The vast, vast majority of people don't really know anything about it, thus pretty much nobody in the chain cares
The complaint I've heard is that Twitch suspends and penalizes streamers for minor violations of their ToS all the time but leave the quasi-porn channels alone because they rake in the views.
This is a bit tangential, but I came across a religious woman on Reddit a while back that regularly uploaded videos to YouTube which consisted of her reading from the Bible and giving her own lectures on Christianity and godly morals while wiggling her toes in the camera. She had a decent following of people pretending that they loved her spirituality while "ignoring" the inherently fetishizing sexual nature.
Her channel was completely devoid of any age restrictions or content warning.
I've thought this too, to some extent. The thing is though, twitch has a lot of young viewers. I don't know the numbers but I'm sure ther are also a lot of young men. This kind of behavior can be predatory (it's debatable how much I blame the streamers for this), and can install some anti-social beliefs about how relationships with people work.