Coax can be TV only because it's like old coax for an antenna or old coax that was hooked up to a satellite system or some other system that isn't connected to like new coaxial cable wiring.

Times when they come in with the cable modem they just run a brand new line right to the cable modem instead of using the existing houses cable TV wires.

Sometimes they wired into the houses TV wiring but basically that's more prone to having problems doesn't really give a lot of advantages since most people don't need to move their cable modem around much.