Because everybody who hears "ground", and has zero decent experience with it, fails to understand that training "for the ground" means training for control of it. That means being able to avoid it and/or use it advantageously.
"If you're a LEO The last place you want to be is on the ground rolling around. I would suggest something more practical...like______"
If you hear that, you're listening to J.C. Pennys security and a JJJ practitioner....at best.