You point out how rural people need to plead and fight for roads nowninder political monopoly, and then tell me we need that political monopoly?

Yep, the governments make unpopular decisions (eg. building 'roads to nowhere') because they are representatives not puppets for the whims of the majority, but if the projects can't get done within term limits then the next elected officials can kill the project.

We need representative democracy because of the tyranny of the majority.

If, on the other hand, we said let the market decide then rural postal service wouldn't exist, as in the case where the major carriers use the national postal services to reach unprofitable areas.