I think they might try it. There are areas in the US where there is practically no OTA signal to be had and many of them do have (or had) access to cable TV.
There are probably fewer dependencies with cable TV than there are with broadband.
My local Comcast is offering a 15Mbps plan for $52/month and I suspect that is their answer to "lifeline service" (even though it doesn't include TV channels). I think the basic OTT service they offer is around $30/month. Lifeline service at $82/month isn't going to fly.
That's something for Congress to decide. At this point, most cable operators have gone the opposite direction because they want to be paid for delivering programming that they have to pay a pretty penny for.