You'd need an immense amount of capital for the network, but also for the legal guerrilla war. Laying fiber to the last mile? What about the risk to the current lines? You get a lawsuit and an injunction while you fight it in court and prepare your impact study that demonstrates that digging a ditch on one side of the road won't cut fiber on the other, and in the meantime who knows how long has passed, probably years.

You probably have to get the city on your side for eminent domain for purchase or at the very least easement rights on a tiny strip of land everywhere so that you can lay cable, and of course that's going to take time, and there's going to be a fair amount of "grassroots" opposition (no one ever comes to municipal/community meetings, you can sway it pretty easily), and so you make your case about how it's going to benefit and bring jobs and bring X to Y group and all the while you aren't actually delivering internet and you're not sure when you'll be able to. In the meantime the existing players can build out in the town you're trying to move into and make the speeds you were promising pointless anyway.

tl;dr: Local government is easily gummed up, you have to compete in many places at once to be a real threat.