Why? Why not use something else? Yes grass can break your fall, but why not use something else? They have the artificial grass some places, why dont they use a carpet there instead?

because i think carpet is not as suitable as grass for our limbs. we fee comfort to grass

With proper maintenance, grass never wears out. It just regrows.

Turf burns and carpet burns are very painful.

Grass is more environmentally friendly.

For 1... grass is low maintenance and cheap

and for 2...

Well... carpet rash is quite painful...

Because the sports were invented to be played on grass.