That obviously adds to the cost of running the airport - see the Prestwick thread for discussion of PIK's problems.
It would close the airport for days on end to commercial traffic if they closed it, PIK has notorious winter cross wind issues. It would be a false economy to close it, BAA sold it off and dug it up in the 1980s (?), I remember walking across it as a ploughed field. It was brought back by necessity.