https://feddit.org/post/3143093

1. Multi-community simulator
2. Defederation avoidance, usually paired with accounts on special interest servers you don't want to risk losing access to.
3. Porn and non-porn.
4. Privacy by dividing online activities between multiple accounts to make it difficult to profile you and to maintain some pseudonymity.

Some on different services, some with different subscriptions, some on different servers, etc.

In my case, somewhat chronological order:

1. First Mastodon account, on server that is unmaintained but still running.
2. Funkwhale
3. Mastodon with full name for academic use, on relevant server
4. BookWyrm
5. Kbin (dead now)
6. New Mastodon for hobby interests, as the server of my first account is worthless at this point
7. Piefed
8. Mbin
9. My professional website is in the early stages of federating as well. Still work in progress, but I follow myself and it somewhat works

If a nodebb forum I have an account on decides to federate I might reach double digits.

Edit: I forgot I also have a Pixelfed account! So double digits already.

It’s not too hard. There are a bunch of different platforms one might experiment with as well as instances. Some will use multiple accounts for different needs or interests. On lemmy, multi accounts are useful for have different feeds, for example. I probably have 7-10. I’ve probably forgotten about a few of them. If you’re curious, it happens.