This question keeps resurfacing once every couple of years or so...
@Jim-Jimjim To give more contest to what @redrum correctly said, back when this map was made TripleA didn't have the feature of hiding players that never actually play. So, there are simply no reasons for the last 5 listed so called players (TripleA calls the powers/countries/factions as "players" and the actual players as "type") to be offered as playable powers to the users, beside the fact that:
1- when this map was made, there was no way not to have players selectable, and
2- so far, nobody updated it.
Anyone can now pull an update to that game (and preferably all of its many mods and variants), to hide (and preferably also assign to the nothing AI) all the players there is no point assigning.