It's really not so thin once the blades (strands) of grass is filled up with that mixture of sand & rubber pellets. Once all that filler is added the field is quite 'spongey'. The old artificial turf used a few decades ago merely had a 3/4" foam underlay between the turf and the cement floor. Yikes!
True. The pre-2003 rug indeed caused a lot of injuries. I marched on it during my high school band days. Always had to lift my knees a bit to keep from tripping over my own feet.