Reply #26: So why weren't they doing this previously?

[Euromutt]

As discntnt_irny_srcsm rightly alluded earlier, there was nothing to physically prevent someone from carrying illegally in alcohol-serving establishments, and the kind of person who's liable to shoot someone over some minor slight like having some beer sloshed on his shirt very likely isn't the kind of person who would obey legal restrictions on carrying in the first place.

Hell, if anything, having customers carrying might actually cool down things a little. In his article "Happiness is a worn gun," describes very well the restraining effect of having a firearm on your person (in this case after having been yelled at by a panhandler)

I’ve never been one to throw down because someone called me a name. But it’s possible that in the old days I’d have yelled something back. At the very least, I’d have felt my blood pressure spike.
This time, I didn’t become angry or even annoyed <...> Rage wasn’t an option, because I had no way of knowing where it would end, and somehow my brain and body sensed that.

I've been there myself. When some guy got angry at me in a grocery store parking lot (I won't go into the reasons, but suffice to say the guy was talking in a raised voice and giving off some very aggressive body language), I really wanted to tell him to go and fuck himself, but because I was carrying a concealed handgun, I felt myself compelled to avoid doing anything that could escalate the situation, and I maintained what I hope was a calm outward appearance and remained polite in my choice of words throughout; I believe the strongest phrase I used was "This is none of your concern and I will thank you to mind your own business."