Kassit,
You will find that most seasoned hangers avoid girth work in an effort to focus more on gaining length. The theory being that the less tunica there is to breakdown the easier the potential length gains.
Ultimately it is about an efficient use of time: If you are working girth you are wasting time that could be spent hanging.
Once they have conquered their length goal they move on to a more exclusive girth routine.
There is also an argument to be made for avoiding the severe stress that one could subject their unit to were they to combine ulis with hanging.
Most hangers incorporate some form of jelqing into their routine, mainly for the health of it.