How can there be no ads? Because your admins are paying for the servers and run them as a hobby. It's not crazy expensive, but it does take up free time. They still do it because they enjoy the communities that develop. These instances are free with no ads because nice people are running them as a gift for you because they like you. Now, is that better than Facebook's or Twitter's business model or what?
@lambadalambda also, small communities can contribute to the upkeep of that server too :) no need nor room for ads here
@kitredgrave I think many newcomers (especially tech journalist types) still think in business models of millions of users. But the reality is that there are hundreds of instances with a few hundred users, and that's much easier to handle.