Let's look at this from the other side of the equation. What do AC's customers get out of CO's route system? Connecting in EWR is no big deal; they can use JFK. IAH is so far from Canada it's practically in Mexico! Ah, but CLE is another story! Connecting there (CO's closest hub to Canada) makes sense for Canadians traveling to United States destinations.
Furthermore, in wintertime they will feel like they never left home.
