I know that Simcoe is a patented or trademarked strain, and Amarillo may be similar, i.e. some hops farm created the strain, and then don't give it away, but isntead sell it, and required that the buyers protect the strain. I may be out in the night, but I'm pretty sure its hard to get rhizomes of this type of strain. The farmers get lots more money for these strains because they own them, and don't want to let them free.
Edit: He who controls the spice(simcoe) controls the universe!