Idk, why do you think mods should get paid? Reddit still has a dedicated team of admins and other that just run the site from the shadows that do banning and removing of illegal/ stuff against tos. Mods choose to run a community and like the feeling of power they get from it. They don't have to run multiple or any, they can always leave it up to vote if they want someone else to be a mod. Being a mod can be full time or it can be 10 minutes a day clearing up your small subreddit. Also each community can have many mods so why should reddit pay those that don't want to add more?