And the primary issue behind that is that a second wire run through the same neighborhood costs the same as the first, and has the effect of splitting users and so cutting profits in half. Therefore it is a natural monopoly.
The secondary issue is that all of the broadband providers have a bad habit of "accidentally" cutting the other provider's wires. It happens enough by real accident that it is impossible to prove in any particular case. But it also happens enough that providers have a pretty legitimate reason to ask that the next provider not be allowed to install wires.
I keep hearing noise (on various urban planning sites - at least the ones that don't suggest getting rid of cars entirely) about how whenever a municipality digs up a street for road work, they should install a tube going down the length of the street for electricity/phone/cable/Internet/any future uses that might require wires in the future. I know of no municipalities that actually do this.
It seems like this is a common-sense solution to that problem. The cost of digging, drilling, and laying building materials is centralized with the municipality that owns the land, who can coordinate maintenance and future drilling with street maintenance that they need to do anyway. It's future proof - if someone invents a great new communication/energy/electromagnetic technology in the future, the last-mile infrastructure to deliver it to residences is already there. New telecom providers need only run wires, a task they already have to do. They don't do digging or have the opportunity to clip each others' wires. It encourages competition.
Wasn't the result of this that nobody runs conduits anymore? "Microtrenching" is the new hotness (aka, let's dig a hole 1cm wide and put a wire in without a conduit, and cover it back up).
The secondary issue is that all of the broadband providers have a bad habit of "accidentally" cutting the other provider's wires. It happens enough by real accident that it is impossible to prove in any particular case. But it also happens enough that providers have a pretty legitimate reason to ask that the next provider not be allowed to install wires.