Part of the problem is that when house builders put multiple TV points into a house they generally use the cheapest components possible. Including the coaxial cable. The Cable system relies on a much more expensive type of coax with better screening.
Cheap poorly shielded coax dosn't matter as much with analogue off air channels, because in many cases the stuff getting into the cable is what you want to watch anyway.
The problem is that these same signals play havoc with cable TV especially digital, so its rare for any existing coax to be used, it does sometimes happen though lazy installers, custs not wanting any more wires around the house, or customers themselves playing after install
Unfortunately the service techs these days don't get much time per job so most new or replacement cable runs get passed back to an install crew
