Not arguing for or against "smaller" clubs being farm teams for "big" clubs but as you live in the States you might be aware that minor league baseball and hockey clubs can and often do have a good following in the town's in which they are located. Not all the teams are in small population areas either. Charlotte, NC, Buffalo, NY, Las Vegas, Memphis and Nashville TN have baseball teams. Charlotte, Cleveland OH, Providence, RI, Toronto and Milwaukee WI have hockey teams.
It gives locals a team to support and a chance to see up and coming talent that one day may be superstars. That being said, I haven't a clue if that would work in English football. I know some minor league baseball teams marketing departments work their arses off doing ballpark promotions in an effort to make sure fans come to games.