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 have a Hotmail account for the same reason. I’ve got a few things that still send to my Hotmail, like government and banking stuff, so I’ve just kept it. Outside of work, I don’t email much anyway so it’s not much to look after 2 accounts.