Not at all necessary...
Who says flying has to be a stuffy, "professional" activity?? Many people fly because they want to go up and have a blast in the sky with their little c 140!!!
I trained at an airport where the instructors wore jeans and t shirt, the students were trained to be excellent pilots (mostly retirees with some extra cash, and some kids looking to go into the bush, as well as some ag spraying interest) I'm sick of the attitude that all aviation must be airline-oriented. The origins of aviation are far from this... that daredevil spirit of the first aviators has been replaced by starched and pressed clones of the perfect airplane "operator".
My instructors wore jeans, and I still developed excellent habits and good flight discipline. I'll wear collar and tie for pasenger confidence when it is required, but otherwise, I'm going to be comfortable.