When I first started carrying it would sometimes take my wife all day before she realized I had a gun on me. Even though it's in plain sight. Now, I barely get my holster on before she notices. One thing it did was make her more aware of what's going on around her.
I think a very large part of the population walk around in a sort of haze. Billions of 'to do's', pins, passwords, phone numbers, and advertising have dulled the general population to what is actually happening around them.