It isn't that simple, at all. Because the roads are owned by the states and communities in which they live. Our digital infrastructure, on the other hand, is based on some very complicated leasing arrangements with various companies that provide internet services. Government(s) cant' just put people on it, because they don't own it.
And, more importantly - put up all the wire you want, you still need a service at the end of that wire, and the ISPs are not running those services for free. Also note that the FCC has stepped back from governing ISPs like common utilities, so the public cannot mandate their policies.