Capitalism, an oligarchy that controls major players, and legislation to keep public players out of the game in a lot of places. Even aside from the fact that private companies are able to prevent municipalities from making their own networks, Congress passed taxes to build out a fiber network and let the ISPs do fuck all, to the point that we had been taxed to the tune of $400 BILLION dollars A FUCKING DECADE AGO.
It constantly amazes me the shit our government lets corporations get away with.