f63 -
In my case (I've got a 1937 pickup) and in most cases with a truck up to at least 1955, the master cylinder is under the floorboard and fitting a booster under the floor is a bit of a challange. I don't know if your's is under the floor or not, but that would probably be a reason not to use a booster for many of the truck owners on this site.
Just guessing!
