That is the story I've heard, too. Even without today's safety regulators, the designers came up with the idea--for safety reasons.
All the ranchers, farmers, construction workers, railroaders, and cowboys probably thought the designers were nuts.
Did you ever try to climb over the shifter and emergency brake lever wearing heavy clothes, coveralls, or boots? :mad:

:mad: After the first try, I'll bet the truck was never locked, or you got the shotgun to reach over and flip the lever.