Each individual actor in the system has less incentive to provide value and no incentive to maintain continuity. As a result, you are basically reliant on a small number of unconnected and pseudonymous volunteers who could walk away at any time. Add to that managing a server with thousands of users is basically a part-time job with little pay and you have a system that is sustained by the kindness of a couple dozen strangers.
That’s why I usually try to interact a bit with my two instance admins on one of my alts. It’s a small instance (less than 100 users at the moment), and I trust them enough that they would warn us and allow someone to take overall if they wouldn’t feel like managing the instance anymore.