@phranck In case you're interested, I did a similar (much smaller) poll in 2020 on the number of used accounts.
https://fosstodon.org/@floppy/105275932107020757
Such polls shouldn't be compared uncritically, but I believe comparison over time will show a trend towards additional accounts for special interests (possibly on themed instances).
I think that is a natural process that might reflect how humans take different roles (identities?) in different social groups. I'm curious how this plays out on the #fediverse.