Sometimes I carry two on my person. When in the car, there is always another plus a rifle. At the range, I always have 2 or more, one being the gun I am shooting and one that is kept holstered and loaded such that I am never without a loaded gun.
The whole Platt and Matix thing of robbing a guy of his guns after he finished emptying them on target is the impetus for always having a loaded gun while at the range. Of course, with a loaded gun or not, Platt and Matix could have still robbed the guy by shooting him while he was focussed on shooting his targets. They did not need to wait until he was empty to rob him, and of course after getting his guns, they shot him and left him for dead, but he survived.
While hiking, I usually have one loaded with regular defense ammo and another loaded with snake/rat shot so as to allow me to effectively deal with threatening snakes, although I have never been threatened by one thusfar. I use snake/rat shot as I have seen far too many and heard too many stories of folks unloading pistols on snakes and still not managing to incapacitate the snake because they were unable to hit vital areas such as the head or the spine directly behind the head. No doubt the inability to hit stems from attempting sighted fire at a distance too close for the sights to be effective (parallax issues) or to scared/nervous/jumpy to make a steady proper shot.