Here, PAX 61 has local commercials. This is probably the main reason PAX wants the local channels carried. They run mostly national ads but have slots for local. These are from local advertisers. Most that couldnt afford to get their ad run on the network stations ABC, NBC, CBS, FOX, Comcast then UPN57, WB17, WGTW (Ind.) have a last resort of advertising on PAX. Of course, they also advertise on radio, billboards, everywhere else, but for TV there is only a handful of places for local businesses. I think Univision and Telemundo stations require advertising be done in Spanish. PAX's rates are pretty cheap I think considering the ratings for their shows are lower.
Even if nobody is watching PAX, when we change channels doing commercial breaks on ABC, NBC etc., there is a chance will see the local commercial on PAX when changing channel up/down, so I guess that incentive enough for some businesses to pay to get their ad run on PAX. Other than that, I dont think anybody cared to see their local PAX.
Some local PAX have schedules considerably different than national, and get few local or syndicated content also I think.