Because the fixed cost of deploying infrastructure (digging the fiber to the house) is extremely expensive compared to the marginal cost (of serving data over a

Because the fixed cost of deploying infrastructure (digging the fiber to the house) is extremely expensive compared to the marginal cost (of serving data over an already installed fiber). 20 different companies all digging their own fibers to the same house would be tremendously wasteful. https://en.wikipedia.org/wiki/Natural_monopoly https://en.wikipedia.org/wiki/Natural_monopoly