I'm honestly asking. So if the government isn't going to maintain roads and let people use them for a reasonable price, who is? What is to keep a company from buying all the roads in a city, which everyone inevitably relies on, and charging some huge toll and hardly maintaining them?

Free capitalism works when competition is possible. With roads and often trains and utilities and other things, competition is not possible. If I own the road that services a certain block of a city, I have a monopoly on that road. And there usually isn't room for another company to come in and build another. Or take trains. If I own the New York City subway system, I have a monopoly. Another company could come in and build a competing system, but all the new lines would have to be elevated or underground because they probably couldn't buy up enough land on the surface (people wouldn't want to sell). Not to mention the starting capital required would make this a rare investment.

So what am I missing?