Why won’t it? I think user accounts need federation as well, but switching hosts isn’t hard. Lemmy.ca went down a little while ago due to a power supply breaking. The admin has been great about it, moving away from the provider that took a day to fix the issue. But during the downtime I was able to use an account I has already set up on a different instance.

When reddit is down, it was really down. When a lemmy instance is down you can just use another. Don’t get tied into just one host.