Economies of scale likely plays a large role. Canada is a very large country (2nd largest by area) and very sparsely populated (same population as California).

Economies of scale likely plays a large role. Canada is a very large country (2nd largest by area) and very sparsely populated (same population as California). It simply costs more per unit to distribute food over such a vast area. The Northern climate and distance from growers also limits the availability of certain foods.