These are private companies. But since they're considered natural monopolies, they are more highly regulated than a typical company.
0 - Yes, I know, it wasn't perfect or even "great" most of the time but that was largely because the incumbent carriers dragging their feet on doing literally anything and the FCC not enforcing the competition rules. And when, largely out of spite, the copper-based incumbents simply didn't do anything to upgrade their networks while the not-at-all-regulated cable companies blew past them in speed and reliability, people switched in droves which gave the incumbent phone companies even more reason to throw up their hands and say "not worth it."
When telephones were first installed, competing telephone companies stringing wires sprang up everywhere. Regulation put a stop to that.
But ISPs are not, generally speaking, a monopoly. There's usually at least two wired options and they compete with cellular and satellite options. Profit margins generally reflect this. The large ISPs are around the average for the S&P 500.
Per https://www.fcc.gov/internet-access-services-reports approximately only about 25% of census blocks have two or more providers for wired internet. Often within a census block most households will only have one option.
https://arstechnica.com/information-technology/2017/06/50-mi...
For my home, 2.5mi from the Capital Building in Washington State, I'm offered four wired broadband providers: 1. Comcast, "advertised 100mbps to 1gbps" (true enough, although you can only get 150mbps, so I'm not sure if that's bracketing) 2. CenturyLink, "25-50mbps" (CenturyLink's own website says "Our systems indicate that our High Speed Internet is not currently available at your service address." I tried several other streets in the area that indicated that none of them had availability either.) 3. Platinum Equity LLC, "10-25mbps" (err, Platinum Equity is an investment firm - oh, one of their portfolio offers "T1 and Bonded T1" lines to businesses and after further investigation would offer me 192K SDSL as a residential offering) 4. Integra Telecom Holdings, "3-6mbps" (a Vancouver telco that does business fiber). So there's one - Olympia, WA.
Everyone else has a subpar coaxial connection from Comcast/Cox/Spectrum.
The issue is that fiber internet itself is a much better product than non fiber internet. And tell the people who have kids and are also working from home that they can't stream video because an HD video stream is 3Mbps+ and 4 people in a house streaming at the same time at high quality is basically impossible.
Some people also have security cameras streaming upload too. The applications for increased bandwidth are numerous. Remote doctor visits can use high quality video, you can stream things from your home NAS, backups are quicker.
What actually bothers me the most is the rules that (in most places) prohibit cities and towns from offering new municipal broadband service as a competitive offering. This used to be more common in smaller towns that had not been able to get good commercial service, and it adds valuable options and competition, but my understanding is that it's extremely hard for cities who don't already have municipal broadband to start offering it now.