Well, it's interesting.
For example on Yin, after a solid drop at some point the player count stabilized, despite still seeing disappearing accounts, even on the first highscore page sometimes.
Though I can also say I am a part of the reason of existence of such accounts. I sometimes join different unis to see the highscores, player counts, galaxy layout etc.
there are plenty of accounts that are older then 10 years.
Can you read, by Neotinea? OP clearly said about new accounts with nothing built and not even loggedin for the second time.