I think the developers initially created a large number of cities (factions).
But to make sure each one has its own unique characteristics, it takes time, which they don't have. This is a marketing tactic. They release a game with only a portion of more or less playable factions. While we are enjoying Heroes of Might and Magic VI, they:
-make money from the initial release
-fix the shortcomings
-develop a more or less playable add-on
-make money from the add-on
-fix the add-on
-develop a more or less playable second add-on
-make money from the second add-on
-fix the second add-on
Цикл "Закадычные враги": "Особенное гостеприимство, "Супероружие", "Меж молотом и наковальней"
"Падение Шантири"
Кампания для "Кодекса Войны"
"Выбор Сагиттеля"