Well, the market providing higher salaries to educated people does encourage parents to invest into education for their children. But the other two points we are in agreement about.

Road safety is also something the local government should take care of. I was specifically talking about federal government, of course local governments have a role as well. For example, making sure to persecute criminals. Providing courts for civil suits, etc. It is not clear that the market would provide solutions for these services.

What is not clear is that the postal service should be national since the market already has several private services. The government can contact you via the internet for official notifications and send your driver's license by UPS or Fedex.

So the libertarian position is that things that have good private solutions should not be duplicated by the government at the taxpayer's expense. The increased costs of things like sending mail will be offset by lower taxes. This is more fair as the people who send more mail will pay more.