Here are some very good reasons from someone in the business since the '60s.
Originally Posted by Guntrainer
Having been in the gun business since before the '68 GCA, I can tell you I have had numerous loaded firearms pointed at me by "show and tell" permit holders. This ticks me off, and I will generally ask the person to holster or leave.
I assume EVERY FIREARM IS LOADED IF NOT CLEARED IMMEDIATELY, and especially if it comes out of a holster or from concealment.
Swept by firearms I knew