This is purely speculation on my behalf as each franchise has the right to choose what they represent & why, of course it is pending league approval. Occasionally a team is located outside a major center and while its fan base lives within the city the team does not reside there, Detroit Lions play in Pontiac & the Dallas Cowboys play in Irving. Neither Pontiac nor Irving could support an NFL franchise on their own. This is common with teams with tradition, the team origionated within the city years ago and with growth, the need for parking, outlying communities made competetive offers with stadium deals and teams moved out and still retained their name, they got the best of both worlds, good stadium deals & a fan base of a major city. Teams with less tradion that have moved or expansion franchises that have set up shop in an outlying community or intend to draw upon a large geographic area for a fan base go with a state or regional nickname from the beginning, such as the New England Patriots in Foxborough Mass., though at one point they were the Boston Patriots. Another common trend is when a state has only one major center, the franchise is commonly named for the entire state: Arizona Cardinals, Carolina Hurricanes, Indiana Pacers etc. Another possibility is when two or more major centers provide a fan base, and indeed the population of both centers was probably a selling point when making the pitch for an expansion franchise: All Minnisota franchises, none can decide between St.Paul or Miniapolis, Texas Rangers play in Arlington and draw a major part of their fan base from Dallas & Fort Worth. The simple answer is that it is the franchises decision to decide who they wast to market their product to, and what is in the best interest of the franchise.