A charger has never been included with a 3DS so it's not necessary to include one for resale.
Maybe in other countries but in NA it's a silly law where all electronics must come with a power cable. I say silly because the regulation is now outdated. It is a waste of natural resources to keep manufacturing power cables. portable devices should be standardized by law to all use micro USB now or the soon to be released USB Type C. This way cables are an optional small price. Already have one from a broken or now useless device, well then you can buy your new portable without one.