[ohtwenty]

I've been using mastodon for a few months and it depends on your instance, really. A lot are more "this is the type of people you'd expect here" (tech people, lgbt people, art peopl, etc) but everything that isn't specifically related to that topic is OK. I'm on a semi-political one, because that's what I'd use a platform like that for. But it's not limited to that at all. Some are stricter, some aren't pegged down to a topic, but might be related to a "type" of person. I know some people who have a few accounts, to only share stuff related to that instance. Some people end up running their own instance (although that's easier with pleroma, you could probably run it off a toaster if you wanted to) or just with one or two friends.

there's added value to the local timeline, especially in smaller instances when you've just joined, because it allows you to find like-minded people. If you could do without that the easiest option might be to join a large instance or start your own, but both come with discoverability issues.

In short, no, you don't need to, but you could (just like you can make multiple emails) if it helps you separate stuff