You are talking Economy 101. I took that kind of course.
In practice, it's more complicated.
Telecom is not a free market, it naturally tends to a monopoly, or duopoly, because of the large barriers to entry, and government regulation.
There's no real competition, and no monetary incentive to keep offering good service once you are at the top.
Again, there might be competition in some pockets, like high density urban spots, but it's harder to have competition as density is lower.
To try and simulate competition through government intervention (forcing to share infrastructure, things like that) seems a bit backwards. It costs money, and only brings indirect results, if any.
Again, my question was, why do we trust the government to build roads, but not internet infrastructure?
(Of course there's the issue of full government control over the infrastructure, spying, filtering and stuff, but now everybody knows that private companies won't safeguard you from a hostile government, they will even provide APIs for your data )