The reason people go to Florida is to escape taxes and expensive housing and then die there. (yes, dark humor, but sooo true). Or for Cubans, to get out of a crappier place. The coastal cities also have the ocean tempering the temperatures just enough so it isn't oppressive hot too often in summer.
It never was a real estate sink to begin with, hence its lax tax code.
Canada is not cheap and has even less tolerable weather, which is not what the grey hairs going to Florida want. I'm pretty sure dying in -10 degree weather in Winnipeg is not exact how someone wants to spend their golden years.
Although, many would appreciate how Montreal's strip clubs are more lax than any place in America.