People like to point to population density but I find the answer a little too easy - about 80% of Canada's population lives within 100 miles of the US boarder and a similar proportion live in one of 3 dense urban areas (Quebec City - Windsor corridor, Calgary - Edmonton corridor or BC's Lower Mainland.) Moreover, network infrastructure was heavily subsidized by the government and service to rural areas remains heavily subsidized to this day.

All that to say, there really is no excuse for how badly we lag behind except for the de facto duopoly.