Then there's no real infection risk if they'll continue to let people drive out of the area, including let people drive a 4 or 5 hours to another airport to make their trip.

Closing the El Paso airspace will reduce the number of people flying, but not stop it, lots of people will make the drive to Tucson or Albuquerque to catch a flight.

I could maybe see it if it was, say, LAX which is a major travel hub, but shutting down a small regional airport without also shutting down ground travel is "quarantine theater" rather than a real quarantine.