Underground utilities make maintenance and construction terribly expensive in dollars, time, and hassle.
If you're in an area where conditions are frequently bringing down poles or wires, it can make sense, but a lot of places want underground utilities for cosmetic reasons --- it's a lot of expense to give you a less flexible system.
That's why you use Dig Once. If you dig, you plan and coordinate, and you make efficient use of the time sink you're putting into laying utilities in the ground.
If you're in an area where conditions are frequently bringing down poles or wires, it can make sense, but a lot of places want underground utilities for cosmetic reasons --- it's a lot of expense to give you a less flexible system.