I would bet that it happened when The ATA came into play. The camoflauge belt, the cheesy clubs, the fact that you progress through like 11 belts in two to two and a half years and can then become a black belt. Also, I was reading about the history of it about a month ago - the founder of ATA decided that TKD too closely resembled JMA, so he added the kicks and limited the hand use in order to give the style a more "korean flavor"