That makes no sense to me? Seattle is just as large as Detroit, and is the 15th largest metropolitan area in the country. It's a bigger metro area than Minneapolis, San Diego, Tampa, St. Louis, Denver, or Baltimore
And Portland (24) is just as large as Charlotte (23), larger than Pittsburgh, Cinci, Vegas, KC, Cleveland, or Indianapolis. The only thing about some of those smaller cities is that they used to be the big population centers back when most people in this country lived East of the Mississippi, and they've had their teams for along time.