[kayodelycaon]

Concrete is smooth and flat. Emergency services have easy access. If you land at a shallow enough angle, you’re just scraping. Given how many planes there are in the air, gear up landings on a runway are well understood.

Plowing the plane into a soft, uneven surface is far less predictable. You never know if you’re going to hit a stump or large rock hidden by grass.

It doesn’t make sense trying to save the air frame if you’re going to risk destroying it and killing the pilot in the process.