I find it in a lot of shops.
Many people are risk avoiders at all cost. Rather than applying risk management techniques (which would tell you an unhandled, holstered and/or concealed firearm CANNOT hurt anyone) they apply avoidance, thinking that "no guns" equals "no accidents".
And you can talk until you're blue in the face; it won't change things.
The range I shoot at has a no-loaded-firearms policy, but it's convenient to go there, whereas I wouldn't go as often if it wasn't nearby. However, when I want to buy something, I go to a different dealer who doesn't have that policy.