The point of Cancun is entirely winter weather in the mid-80s at a more reasonable price than Hawaii or the Caribbean islands; anything involving authentic Mexico doesn't factor into most people's decision to vacation there. Even in Key West or Miami, Florida winter weather can be a bit hit or miss from December through February if the point of the trip is to just sit on the beach in a bathing suit.

It's the North American equivalent of cheap British package tours to the Canary Islands. Lots of folks seem to like that kind of thing, but I'll just go ahead and take a pass on that experience.