Many LED Christmas lights ARE polarized. So are many lamps. Double insulated devices are the onlyones that can get away without polarized plugs and MOST wall warts fall into that category. More and more double insulated tools are also getting polarized plugs, at least here in Canada. It is legal to sell these load devices without polarized plugs, but at least in Canada there are no non-polarized 2 promg outlets that pass CSA standards or ULC (Underwriters Labs Canada) certification - and without one or the other they cannot be legally sold here. Don't know for sure about the USA, but suspect the same is true there.