Fame
There are too many unprofessional people swarming into the industry for the work to get much fame. And really, do young kids dream of being arborists? Sunday Night ArborBall doesn't sound like a winner to us.
Only a few arborists have the distinction of working on trees of historic significance, and being known for doing it properly. Even then, they only get the glory while doing the work, but are forgotten the next day by Joe Sixpack. Does anyone know who takes care of the Atlas cedar at the White House where President Carter built the treehouse for his daughter Amy? (Or care?) Who took care of the tree that grew in Brooklyn; or the Treaty Oak of Texas?
Somehow, we all know that George Washington cut down his father's cherry tree; but he wasn't even an arborist.