Why?
Because everyone knows that there is a good chance the person that just accidentally bumped into you is carrying. So rather then a extended period of chest thumping that devolves into violence the bumped says "Hey!" to the bumpee. Who, knowing that the person he bumped into is also probably carrying, says "Sorry!"
There is no, "What is this little guy doing" or "Big guys think they own the road". They know that when it comes to fire power they are pretty much equal.
There is nothing to be gained in status by taking it further. No one is going to think any less of the two because they let the incident drop. In fact by taking it further you have lost points on the social ladder.
And that is, in brief, why an armed society is a polite society.
After Hurricane Ike hit the upper Texas coast, the rat media types asked the Governor of Texas about looting in Galveston county. The head of the DPS (state troopers) answered that question. He said that is no looting in that county. Galveston county has the highest per capita of CHL license holders of any other Texas County.
An armed society is a polite society.
There was a group of guys that put up a picture on the internet. It was a piece of plywood spray painted with the message, “you loot, we shoot”.