Not all the value going over those lines is created by the cable company.
In fact, very little of it is, and it can only exist on the vast majority of its path with taxpayer support.
In any case, in the United States, theft of service is generally treated as a criminal matter. I don’t see why this should be treated any differently, or how it would be fair to single cable companies out for exclusion from protection for having their service taken for free. Inn Keepers, other utility companies, and many other businesses enjoy the same or similar protections for their services.