Hm. I just answered your question, which you had stated was a serious question. Is it natural for chickens to walk around on grass and soil? To an extend: natural would probably be having some vegetation under them and a few spots of bare soil here and there, but they would move around more, so...
Soil gets compacted quickly and does not absorb and evaporate moisture well. Consequently it provides a breeding ground for bacteria.
You want a material that is absorbant with lots of surface to give the moisture off into the air again, that will keep the brooder dry and stink free.
I am sure not more people use it because it is very hard to get here. I believe hemp growing was lumped together with growing marijuana and outlawed (this is not researched, just something I believe I read somewhere sometime). If I want to get hemp bedding I have to have it shipped here and it...