The company pays but then it can also use other companies' fiber, so sometimes it's worth it to do so in order to show that they have coverage in a certain area where there might not be fiber (that they then lay down), and also that they cover everywhere else.
It's quite a clever system that uses market greed to incentivize building. It's the same system as railroads, imagine if railroads could not share tracks with each other.
Some places also vote to have the city or town connect with Fiber which then puts tax money aside for it.
In many places it is the power companies that run fiber and they are mostly partially or fully state owned. The lagest ISP also has the state as the majority share holder.
It's quite a clever system that uses market greed to incentivize building. It's the same system as railroads, imagine if railroads could not share tracks with each other.
https://en.wikipedia.org/wiki/Arrangements_between_railroads...