I have mixed views on this. On the one hand, a club provides an instructor with a uniform to give a good image - and as many instructors aren't exactly paid minimum wage, then it would seem unfair to make them buy the uniform themselves. This is especially true at the airfield I fly from which is very muddy during the winter months, and you wouldn't want to be destroying your own clothing.
On the other hand, a line should be drawn somewhere. Wearing the ol' gold stripes in a PA28 (or worse a C152) is a little pretencious IMHO. I certainly wouldn't do it if I was in that position as it seems to be a symbol of superiority - teachers in schools no longer wear gowns and mortar boards do they?
The approachability of an instructor is basically down to their attitude. If they are not approachable, and cannot talk candidly about (flying) problems with a student, then they shouldn't be an instructor - and I don't think the argument that they are just their before they get their right hand jet seat is a good one. Their sole purpose as an instructor is to teach you and I to fly, safely, and be there to offer advice as necessary. Do FIs have to do a course in tuition? (dunno the answer to that, never looked into an FI course). Does any external agency (outside of the flying fraternety) evaluate an instructors ability to teach?
One essential item that should be provided though, that would make instructors way more approachable is a constant deodorant shower during the summer months - nothing like getting into the cockpit on a barmy summer evening with your instructor who has been working all day in the flying greenhouses
Just my opinion, hope no one gets offended......