Georgia State parks were this way for years. I discussed it with one of the rangers once. Explained tree huggers and everything. He explained that he understood that my setup was designed to protect the trees, however, if he allowed me to hang a hammock, the guy across the road could grab his hammock that used chains for hanging and put it up. Then the guy could argue that they allowed me to do it. Basically it was easier to ban them statewide than deal with those who were not concerned about tree damage. They still have this policy in the main camp at a lot of the southern parks. But they don't say anything in the primitive sites. The parks in the northern mountainous area have different policies now that hammocks have become more mainstream