Lack of Convenience Outlets on Ranges
Underwriters' Laboratories (UL) said they had to be eliminated because the types of appliances plugged into the outlets did not have three prong cords so an ungrounded appliance plugged into an outlet on a grounded range would, if there was a serious current leak or short circuit, ground to the range making it electrically live and a shock hazard to anyone who touched it. I think that was about the same time that push to turn surface unit knobs were mandated.