E: see this video https://youtu.be/bGvfYv5nzs0?t=138
E: see this video https://youtu.be/bGvfYv5nzs0?t=138
"Good UI" doesn't make something a platform.
Doing payments in a fee-minimizing way definitely doesn't make something a platform.
This isn't like a newspaper, finding neither ads nor paywalls will make ends meet. They're not phone app developers, finding users will barely pay $1. It isn't an ad-supported business that can only make a fraction of a penny per user. Their moderation needs are at a pretty small scale, with most user accounts tied to known bank accounts. They don't have to negotiate with rights holders for copyrighted content and get taken to the cleaners. They don't have to store and distribute gigabytes of video per second. They don't face big customer acquisition costs.
Youtube and Twitch are doing a lot more work for their cuts.