Put up or shut up!
What fry's my balls is that these private corps don't want to invest, but they won't "let" anyone else do it either. The AT&T days of the 1970's haven't changed much in some regards.
I am almost always against govt spending, but our society is becoming such that fast and reliable Internet access is as essential to some of us as roads and bridges are to others.
Maybe an alternate approach could be that under served areas could instead work to bring in some other private company to build and run a network. Things like this are routinely done when baseball stadiums, etc are built. Govt often bonds it over x years, with the revenue projections to cover all of the costs of the bonds. Still some risk, but may be better than 100% govt run.