[gerbal]

I think it's that power companies depend on a very broad customer base to support their substantial capital investments. When you start removing a small portion of customers the cost of power to everyone else starts going up. And if those customers aren't consistently off-grid, i.e. they still need grid power sometimes, that can actually raise power costs.

Increasing generation capacity to meet demand spikes is expensive, and requires having large, expensive power stations waiting at the ready, just costing money.