my perspective on this is nuanced.
generally speaking, if you are rendered a service, it incurs a cost to render it, and you're either paying for it in cash, or you're getting it for "free" in return for seeing adverts. if Mastodon was ever to scale up its 1 million active users to the level of Facebook, with 3 billion active users, costs would probably go up orders of magnitude.
as it is right now, individuals in the tech community provide this service for free, and the costs are relatively small. if the general public ever starts using it, non-techie users are going to grow quicker than techie-users, and expenses per server/techie are going to go up.
there is a possible model where everyone holds Wikipedia style fundraisers, but this, too, is technically speaking a form of advertising.
you've got to ask the users for *something* ultimately.