Not all kenpo schools teach the art against static attacks either.In contrast Kajukenbo was designed as a self defense system to be used against street attacks. In the time of it's creation and for the most part today, most street criminals did not have any formal martial arts training. The ones that were skilled were either the guys from the poor neighborhoods who boxed as kids and teens, or guys who were just plain mean and vicious.
Besides being martial artists, the Kajukenbo founders (at least 4 of the 5) were also boxers, who knew that the majority of real fights weren't going to be won with one punch.
They also knew they were not going to have a street fighter attack them with a step in lunge punch to the solar plexus. When you get in a fight, someone's going to try to punch you in the face, break your nose, break your jaw, knock you out.
With this in mind they designed the Kajukenbo punching defenses (Punch Counters) and break holds (Grab Arts) to be done against a variety of punching attacks that are targeted to the face. Punch Counters are done against a right cross, left jab/right cross combination, right cross/left hook combination, etc, etc.
Many of the Grab Arts are done against someone who grabs your shirt and hook punches, grabs your shoulder from behind and turns you for a right cross to the face, etc, etc.
Somewhere down the line from Gascon, Pesare, Cerio, and Villari, things changed. Sometimes change is good, and sometimes it's good to re-examine what was changed.
Sean