Leaving you with 80% of the revenue you, yourself, directly generate is unheard of in this day and age. If you have anything like a 9-5, you're probably getting around 10-20%. The rest goes to all your bosses, and most importantly of all, the company shareholders.

20% is considered low

All others take at least 30%

Maybe. Without it, though, the individual would have to build and maintain a site, direct traffic there, and handle payments, as well still do all of the community management and content creation they already do. Now either they'd spend their own time doing this if they have the knowledge, or pay others, which might meet or exceed that 20% depending on their income level.

Doesn’t Spotify offer like .5%