We already have physical networks. Maintaining them is a fixed cost.[1] You can't eliminate it because you can't reasonably expect to replace the entirety of Cable TV and U-verse with cellular, so the money might as well be going to maintain fiber rather than copper.
I'm not trying to be sarcastic here -- this is how the government thinks about things. We have an existing infrastructure that is less than optimal, but it still functions and is in no danger of imminent collapse. Contrast with our healthcare system which barely functions and is on the verge of effective collapse. Or our public schools and police departments, which have collapsed in a number of cities.
In short, it's hard to drum up political support for large infrastructure projects even if you can show the need. There has to be a demonstrable catastrophic impact if we don't do the project, which just isn't the case with broadband.
You're right; and costs to maintain copper run about 5-10% of initial costs PER YEAR. Physical networks with lots of endpoints are very expensive to maintain.