Just for the sake of illumination.
The screenshot of player populations above, is misleading.
Those account primarily for console players, for which only a limited number of Persistent Worlds is available.
By all accounts there is a particular approval process that worlds must follow in order to be available to console players.
I'm going to look into it...
See the following comment by Julius Borisov (Beamdog developer), and the surrounding thread for further details: