A quick perusal of Wikipedia reveals the following:
Metropolitan Area Population
(Not to be confused
Winnipeg, Manitoba 694 668
Hamilton, Ontario 692,911
Quebec City, Quebec 715,515
Atlanta, Georgia 5,290,078
Phoenix, Arizona 4,192,887
Kansas City, Missouri 2.2 million
Las Vegas, Nevada 1,951,269
Seattle, Washington 3,407,848
Hartford, Connecticut 1,188,241
Yes, there is a built-in immediate fan base in all Canadian cities for hockey. However, why would any profit-driven organization EVER move a franchise out of a city with 4+ million people to a city with only 16% of that population?
It is the difference between having an immediate and steady but perpetually small cash flow and having a small initial flow with enormous future potential.
Of course Gary Bettman and the NHL are fighting like hell to keep hockey in Atlanta and Phoenix and aren't jumping at the chance to return to Winnipeg or Quebec City.