I mean, you could ask the same thing about electric utilities. What's special is that as a society, we've decided that we don't want dozens and dozens of companies running infrastructure through public land. We grant some private companies space, for rent, but that also comes with the burdens of public process. In more space-constrained areas like telephone poles, streets, and conduits, it's often better to have a small number of companies utilize the space, but at the cost of additional regulations.
Electric, gas, phone, and water companies have captive audiences, but at the same time need the PUC to approve rate increases and are required to meet certain performance guidelines.
I'll also ask for the third time: Why should ISPs be different than the phone company?
For the record, I didn't address your "space-constrained areas like telephone poles and conduits" before because neither is remotely space-constrained (especially in the fiber age), and this is a complete red herring.
As long as they own the physical network they should be a utility
If phone companies blocked you from the Butterball hotline because they support another turkey company, that would be what's known as an "anticompetitive business practice". Now, if you removed the special exemption telecoms get, the FTC would fine them for that, and tell them they can't do it.
In the same way, if ISPs were to prioritize their own video services or block a competitor's, that would also be against antitrust law, and the FTC could fine them for it. Hilariously, the common carrier designation actually prevents this from happening.
At the risk of aggravating the moderators, to ask this a third time what is so special about telecommunications companies, that, unlike other monopolies, need a whole different form of regulation?