"... a significant portion of the #Fediverse, at least for now, runs on pure enthusiasm, and sometimes on donations from supporters or some occasional banners. There’s currently no sustainable commercial model here, and it seems that there is no intention to implement one yet."

https://www.kaspersky.com/blog/what-is-fediverse/48916/

Why would we? A centralised revenue model for... 

"... an association of independent social networks..."

...is basically like trying to create one for everything on the web. It's bananas.