Because moderating can be a full time job. If you go for a vacation, have a family emergency, etc and aren’t actively looking at your instance, then it’s “left to rot”.

If it’s possible, doing the steps OP mentioned before going on leave will help the server avoid getting into a mess while you’re gone.

That doesn’t mean anything. For example, WhatsApp is “using the signal protocol” but is very much a walled garden.

What’s wrong with just using matrix?