It’s free*, insanely easy to set up, you don’t have to worry about port forwarding or ddos or hosting fees, has powerful moderation tools, and there’s a plethora of easy to deploy bots that help manage permissions and automate routine tasks. Literally, if it had a proper web-accessible forum similar to phpBB, it would be perfect.
You know it’s coming. Why would a streaming company want a consumer buying one month, binging a single show they’re interested in, then immediately cancelling the subscription after, when you could guarantee a 6- or 12-month revenue stream for them?