Twitch is a gaming site. Kids watch youtube videos of people playing games, they get funneled to check out the minecraft/fortnite/etc. category on twitch then they get curious and check out the large streamers on the site. What do you know? There's a streamer who is sitting in a hot tub with 20k viewers (enough to put her in the top streams). It doesn't matter that twitch has a "mature audience warning".

Anyone who has used the site for any amount of time knows Twitch is providing a clear on-ramp to underaged kids accessing nearly-softcore porn.

They can't have their cake (young, gaming advertisers) and eat it too (allow nearly naked young women in kiddie pools) on the same site... Only reason they are even being forced to make a change is because of advertisers. I can only imagine if parents actually knew the extent of the hot tub streams, twitch wouldn't be allowed in a lot of households, but since its a "gaming" site first, its under the radar.

A vanishingly small group. Most people aggressively seek that shit out as soon as they hit puberty.

It's like a TV channel. They'd never show actual porn but they try to get as close as possible while retaining plausible deniability.