and why do you only have comcast as a choice? Government granted monopolies. Void all local contracts with ISPs (cable or telco), and you will have choices.
To entice them to invest in their area because nobody else would.
Infrastructure isn't software development. It requires billions of dollars of capital investment. That investment isn't going to go to many areas unless it's nearly guaranteed a return, hence the labyrinth of monopolistic guarantees bestowed upon ISPs.
It's not clear to me that consumer options would flourish if you were to roll back all ISP related regulations and void existing contracts. I suspect the current system would just become more entrenched.
No, companies will go with the cheaper route i.e. continue the comfy collusions they have now. You're insane if you think they'll magically start sharing their own infrastructures with each other.
The first build out of fiber to the curb is expensive. 2-N is cheap if you do it right.
Or maybe you're saying that private ISPs will perform the deployment and then share their fiber? Which seems wildly unrealistic.
firms specialize, it's an important attribute of a functioning free market. If there is demand for running fiber through conduits, local firms might specialize in that type of construction, especially if local knowledge and working with local governments can be leveraged across customers. Many industries are not vertically integrated where specialization is more efficient than vertical integration. (i.e. Ford stopped making tires and glass)