In this day and age, just about every hub is really a focus city. The two most notable exceptions are, IMO, Salt Lake City and Charlotte. Those two large operations for DL and AA, respectively, wouldn't be there if not for their primary mission of connecting traffic. Instead, the biggest mission of a hub is to dominate (to the extent possible) the O/D market of very large metro areas. Over the years, the number of what the industry calls a "hub" is declining, not increasing. DL-Memphis, AA-Nashville, UA-Cleveland, AA-Las Vegas, AA-Pittsburgh are all former hubs that come to mind.

So what's changed? Primarily, it's the capability of modern aircraft that has, in some ways, revolutionized air travel over the past 20 to 30 years. Looking back 30 years, only turboprop aircraft could reasonably service smaller airports with anything that resembles frequent service. Those turboprops didn't have the range to fly long distances to far off airports nor did they have the passenger comfort that anyone would want for an extended flight. This is why all these hubs developed; to service these small-ish airports with frequent service.

Those limitations have been removed for just about all domestic travel and a portion of international travel, too. Along with the elimination of turboprops, It's noteworthy that the NG series of the 737 was the first of that a/c type that could reliably handle all transcon routes. Some here may remember that a 737-300 could fly from Washington to the West Coast only with a reduced load. No one thinks about that kind of restriction today. Heck, I read Breeze is going to start LAX-CAK service which would have totally impractical years ago. It's really only the introduction of the A220 that permits such a long and thin route as this.

The question then becomes With all the advancement of a/c capabilities, does UA really need to invest a very large sum of money in another hub? I think the smart answer is "no" unless they think they can do it for the development of a substantially underserved potential focus city. I don't think such a city exists in the southeast. And what markets would UA be trying to serve that they can't now that regional a/c can handle most any market without a connection?