If the descentralization of social networks continue, we will have to prepare for the eventual rise of the instances wars, where people will start to fight about which instance is better and which one is weird to be in and so on, but that’s for the future of us all.
I’ve got multiple accounts because I have my main (this one) and an account on feddit.uk. The account on feddit.uk exists because I wanted to make a very UK-niche community on there, and I believe you need an account on an instance to make a community on that instance. I could give up my feddit.uk account now, but it’s nice to keep around in case my main instance goes down for maintenance or some such.