In the case of our flight, we (as well as any of the other "entitled" passengers on the flight) could have chosen between AC, American, or Westjet for direct flight options. Each of the carriers offered a flight within about an hour of each other.

We all chose AC. This could've been for a variety of reasons, including price, quality of product, loyalty programs, etc. Anyone also could have chosen the other options available. Instead, we were delayed by 4 hours because we chose AC. Like I said, I get that delays happen. But we would have been on time had we chosen to travel with the competitors. I don't think it's unreasonable for AC to offer $15 vouchers so that customers at least have some choice.