I've worked in shops, although not music shops, myself.
In my experience, a large proportion of customers were rude, impolite, impatient, self-centred and think that shop staff are robotic pieces of sh1t for the customer's preferred and immediate use. I know other shop workers who have had the very same experience.
Over many years, I've always had good service at GAK in Brighton (except on one occasion a very long time ago when a member of their staff failed to relieve me of £400 cash in my pocket because he couldn't be bothered to stand up).
I've also been well looked after at a wide variety of other music and non-music shops around the country.