Installing wires requires digging up roads, using utility poles and leaving utility boxes on other peoples' property. You need permission from local government to do that, period. In some places, the local governments only give one company permission to do that. That's a government granted monopoly. In other places, they give permission to more than one company, so that they can compete with each other. That's a government granted oligarchy. But whether there's one pre-existing cable company or five, if you want to start a new cable company, you need government permission, and you probably won't get it. It's nothing like a free market.