I think one thing we tend to overlook is that British Columbia is far and away the most diverse province, with oceans, rainforests, mountains, cities, and Canada's only desert. It naturally would make sense that it always hosts 2-3 legs.
Sure, we have the territories, the prairies, Ontario, Quebec and the Maritimes, but it would be pretty hard making a full 11 leg race that excludes BC and also makes each leg feel unique, in the geographic sense.