I was brought up in the "bush flying" environment in Northern Quebec in the
50’s and 60's and was always told to dress (and have your customers dress) as to be able to: "stand around looking stupid for 24 hours" in case the damned thing burned with all the survival equipment aboard. A knife, Zippo Lighter, compass, ect were also recommended.
I once had 3 customers show up for a trip to the "outreaches" to view a mining prospect get off an executive jet dressed in suits and ties - in November in Northern Canada no less - I refused to depart with them and after a brief discussion where the words "I'll have your job" were used. I asked them to stand on the ramp for 10 minutes - after about 5 we made a trip to a local store and bought appropriate clothing for all.
I have found it to be a very good concept