[jhall1468]

> You can also fly. Skies are more 3D than digging and easier to access

Easier, yes. Cheaper, no.

> At some point the holes could cause collapses.

The risk is extremely low, and car accidents have caused a vastly greater number of deaths than any other form of transportation.

> There's also water mains and other hazards and obstacles.

Pretty sure there were some pretty massive hazards with flying too.

> Sounds dangerous.

Which a lot of people said about flying as well. And it's vastly safer than a car.