More than 4 decades of flying for my living, both military and commercial, during which I was required by the job to "look the part". The only situation which justifies private pilots having to present a similar image in my opinion, is when flying through Third World countries where, as Glasgow_Flyer suggests the natives might be impressed.
These days while involved in PPL activities, I wear flame-resistant coveralls to keep the dirt off my clothes during aircraft inspections. What a t....r I'd feel if I adorned myself with regalia!