I'm thinking this happens a lot because the dealers hire folks that really don't know much about RV's. I, for one, do not know a lot about RV's, and found out the hard way that they will put a switch for a light (or whatever) in the strangest spot!
I tore into the panel just inside the entry door of my 2017 27' XLR Hyperlite toy hauler looking for the cable line from the TV. I couldn't get the TV to work at all, or I couldn't get ANY reception, just a fuzzy, snowy noisy mess on screen. I was able to trace one of the wires inside the panel that 'seemed' to be coming from the rotatable antennae on the ceiling that's just inside the door. The wire went all the way back across the ceiling to the bedroom!! As it turns out, that wire actually powers the manual antennae so that it sends the signal to the TV. There is a tiny push-in-ON, push-in-OFF switch beside the TV mount in the bedroom, with a tiny green light that "turns on" the antennae, and sends a signal to the TV. VOILA´, I HAVE RECEPTION FOR APPROXIMATELY 50 CHANNELS just from the little roof antennae!!
Trying to put the panel back was another story !!
Mark