I started on lemmy.ml, as I code a lot. I got a lemmy.world account when I found a lot of communities there I wanted to join and a lemmy.studio account for music communities. That was a few min before I learned how to subscribe cross-instance. (I couldn’t find the communities) I could clean up teh accounts, but nah, couldn’t think of a reason why.
Now lemmy.world is my main instance with lemmy.ml as 1st backup and lemmy.studio as special interest. (and I found a Dutch instance)