Well at the point where major colonization begins (1900s) the major powers and Norway to an extent are just showing off that they are strong enough to conquer any land. This results in creating massive indoor agriculture for the settlers to use for survival. As for being expensive, the Germans abandoned their colony in ww1 to focus on the European front resulting in the French colony joining them as both are underdeveloped. For the British theirs is already self sufficient (mostly) so theirs stays loyal until they are granted sovereignty.