As others noted, this is largely a CYA clause. I suspect the real reason is because UAVs are a legal grey area as far as the FAA regulations are concerned. It is generally accepted that regulations for R/C aircraft also apply to UAVs. The tricky point is that the FAA regs specifically state "for recreation". So you can legally fly an R/C plane and take aerial photos as a hobby. However, if you sell those photos then now you've broken the law. (R/C clubs recommend selling one ground photo and giving away the aerial ones to skirt the issue). The AR.Parrot folks know the regulations and are simply trying to distance themselves with boiler plate.