I think part of the allure of private chats is that it's you & a small group of people who actually know each other - having a free-for-all and just splitting rooms up doesn't engender a feeling of togetherness any more than going to a random gathering of people with a single 'banner' topic. Twitter almost has the hashtag thing down.

Human social groups have a purported manageable upper limit of around 150 people, so super mass networks like insta, facebook, twitter etc also get to 'broadcast' level interactions rather than intimate discussions - it seems as though private group chats are a way to have a digital campfire, with less pressure & more shared experience.

There's so much behind building a social network that it takes a perfect mix of luck, timing, skill & marketing. But they will continue to come, won't they.