It depends on the locale as well. The sand where we live is very easy to dig in (unless it's too wet or too dry, which is 80% of the time).
Go 100 miles west and the ground is either limestone or granite. Very unconducive to underground installations.
It's easy enough to hit something when you drill a hole for a pole. When you trench, you hit sewer lines, water lines, gas lines, pipelines, and (oh yeah) other electric lines. Nothing comes cheap!