[amatecha]

probably because my username is my first initial and my last name, and I don't really want someone impersonating me on a platform that I've used as a key social media presence since 2007?

[Sunspark]

If it's a key social media presence for you then that means you're logging into it and using it, so there is nothing to worry about.

[amatecha]

Right, but if I delete my account, and someone takes my username, people who have known me over the past 15 years will probably think that's me (and whoever takes the username can very easily exploit that fact). Username reuse enables impersonation.