Yes, in 1976 Congress passed new legislation that forced them to pay up. By that time the cable industry was well-established and could afford it (and they had enough of an audience that the broadcasters had a strong incentive to make rights deals). If the same rules had been in place and enforced in the 50s and 60s, I doubt there ever would have been a cable industry.
The important thing to note is that the cable companies won the lawsuits (with the arguments that are currently being made here, the courts agree with you!) which spurred Congress to amend the Copyright Act so that transmission was a copyright violation and cable companies needed to license.