In a perfect world, an affiliate would run all of its network programs. But there's a little thing called ratings. To cite one example, in the late '70s, NBC was placing show after show on the bottom of the Nielsens. WSB Atlanta was spending beaucoup bucks to replace those shows with movies and syndicated programs in order to maintain its top-rated presence in Atlanta. It turned out to be a factor in the station's moving to ABC, whose stronger lineup meant fewer pre-emptions and less drain on the station's bottom line. Likewise, for a couple of years (1972-74) WSB was the only station in Atlanta carrying its network's 4 PM show in pattern ("Somerset"); WAGA reran "Bewitched" and WXIA ran movies. Seeing the revenue 5 and 11 were bringing in, Channel 2 had no choice but to put on a syndicated show ("Mod Squad") at 4.
And Avid is right; most people probably don't notice if a show is network or syndicated; I suspect viewers in Raleigh think "Wheel Of Fortune" is an ABC show; in Greensboro, they think it's CBS; in Charlotte, NBC, because those networks' stations carry it in those markets, respectively. Likewise, I suspect a whole lot of viewers around the country think "Judge Judy" is either a CBS or a Fox show, since those networks seem to be in the majority of her station lineup.