Here's why:

* Crust: The outermost layer of the Earth, relatively thin compared to the other layers. It's where we live, build our cities, and extract most of our resources.

* Mantle: The thick layer beneath the crust. It's solid but behaves like a very viscous fluid over long periods. The extreme pressure and heat make it impossible to mine or drill through.

* Core: The Earth's innermost layer, composed of a solid inner core and a liquid outer core. The intense heat and pressure would make any drilling attempt impossible.

While we can dig deep into the crust, reaching the mantle or core is currently beyond our technological capabilities.