my guess is it’s the same rewards that drove people to run usenet servers, bbs servers, irc servers, forums, countless open-source projects, and whatever other non-centralized platforms flourished in the past and present.
Like I said, notoriety and control of users. People ran BBS servers to be sysops, IRC servers to get O:lines, open source projects to get their name out there, etc. "Pure altriusm" could also be a motivator.
as someone who has been significantly involved in open source projects and contributing to hosting for various projects for years, “control” and “notoriety” are rarely what people are getting lol.