There used to be LOTS of unpopular routes before deregulation. Airlines were often forced to maintain service to cities they could not make a profit from and were subsidized by the government to do so. Oftentimes the CAB would give an airline a "good" route in exchange for maintaining service on "bad" routes. For example, Northeast Airlines was given routes to Miami and Los Angeles but had to maintain service to numerous small communities in New England that couldn't even fill a DC-3 or FH-227 on a good day. American used to operate a series of puddle jumping flights through upstate New York from Boston, too.