I dunno what that is, but it doesn't sound like a YouTube thing. Maybe a... what was in called? OnlyFans or something thing.
Yes, they're mostly on Twitch, not Youtube.
They are game streamers who uses their beauty or sex appeals (by showing cleavage) for more views.
They won't be nude, but they will flaunt their chest assets as a way to get followers and viewers.
Some are not even goods in games they stream, but they're more eye catchy and "fun" to watch compared to normal game streamers.
Didn't know that was a thing now. But it does make sense for such a thing to exist for awhile. Though I suppose talent agencies would make it difficult for independant youtubers of the same field to rise up if talent agencies and buying up the attention of the market.
Indeed it'll be hard. It's a capitalist world after all.