might have something to do with the fact that the vast majority of Canadas' population (cell phone users) live in 2 or 3 major cities with vast sparsely populated spaces across the country. Costs for cellular communications infrastructure are probably not sufficiently offset by service user revenues.Cellular service companies are just like all other businesses - they are there to make money. In order to remain profitable the Cellular Communications companies must charge rates that ensure profitability while delivering reliable service to every cell phone user in the country.
Just an armchair analysis of the matter.