A couple observations after reading the thread. I worked for years in cable TV, on both the regulatory side, and later, the tech side.
Yes, the difference between broadcast and cable is the FCC licenses the spectrum broadcasters use, but not the cable carriage, at least in the same way. However, the FCC did implement rules governing the carriage of broadcasters on cable systems, but these don’t cover and wouldn’t affect content obligations, as the rules at least used to (requirements for news, public service, etc.). But they also had ownership rules, which is why Cox, based in Atlanta and owns a broadcaster there, doesn’t have any local cable systems (this was a challenge when I was implementing a system for Cox that my customers - Cox staff - couldn’t experience at their homes because they all had other cable providers).
WRT cable not being infinite - the cities regulate use of the “right of way” but once you get that approval, you still have to deal directly with the owners of the poles or conduits for access, and there are rules about that - where/how wires can be attached, payments, etc. More room could be made on poles but it is very expensive.
Regarding lack of competition - the municipalities generally negotiate coverage, meaning that the cable company must build out all streets in town, or all that meet a certain density. If a competitor comes in, they would have to do the same thing (in part because of Level Playing Field language we negotiated) so you’ve incurred all the expense, but have access to only the same universe of potential subscribers. This is why most “overbuilds” are by the phone or electric companies, since they already have the infrastructure largely in place. It would be economically unfeasible for someone to start entirely from scratch to build a system.
Finally, an interesting aspect of cable regulation is OTT services, even when the cable company is offering them (that is, they have a streaming version of their product). It is mostly the same system in terms of channel acquisition, entitlements, etc. but is just transmitted outside the bandwidth for reserved for “cable,” like all other internet traffic. In these cases, the position the companies took was that some obligations of the traditional cable service like support for closed-captioning, DVS, EAS, and in Canada, sim-sub, did not apply because they came over a different part of the same wire coming into your house (or streaming to your phone via a hotspot).