The reward for the work is the result of the work. For these communities to exists, there must be moderation and for many people the existence of said communities is worth the cost in time/server costs. Reddit selling stock off the backs of people who perform free labor for them is a problem, but someone who sets up a lemmy/mastodon/whatever to host discussion about the things that they care about is not a slave just because they don’t demand monetary compensation or sell your data. The lack of monetization isn’t a bug it’s a feature.