Yea I’d say it isn’t a problem for anyone until it is. All of the notable examples of a server going down that I’ve seen were a surprise to its users. On top of that, I’d expect many have fairly hefty expectations of their server’s longevity. Like 10-15 years, more or less as long as they’ve been using Twitter etc.

It's definitely an issue with small, niche servers unfortunately. Had a friend's just go down unexpectedly this week with no warning to let the handful of people on there migrate, so they're starting over from scratch. My craft server shut down a couple weeks ago although we did get a month warning there so could go through the proper migration process.

I try and donate to all my Fedi servers just to make it worth the admin's while, because I prefer smaller servers in general but don't want them to suddenly disappear!