"Air Canada did it years ago when it launched low-cost subsidiary, Rouge. Passengers complained back then about being packed in like sardines and being “fleeced” for seemingly mundane amenities. Yet Rouge today is a financial success, credited in helping Air Canada’s fortunes soar"

Because on many routes (i.e Las Vegas, Mexico, Carribean or even Los Angeles from Vancouver) ,the only choices are the execrable WestJet or the abominable Rouge!!! 

I try to avoid either one whenever possible by rather flying through Los Angeles to Vegas (which surprisingly can be cheaper than Rouge even with the connecting flight on a US airline) or when travelling on from Vancouver to Los Angeles on business I fly on Alaska which is superior in comfort  to either Canadian airline.