In other action shooting sports, except IDPA, which penalizes dropping loaded magazines, competitors will replace the magazine in their gun before it it is empty so that they don't have to cycle the slide to get back to shooting. Tenths of seconds can make the difference in winning or losing a 12 stage match, and shooting the gun to slide lock is much slower. The only time you will see a serious competitor shoot a gun empty is if he has made a mistake. At that point, the competitor has made such a serious error that the stage is a total loss, it's just a matter of doing the best you can at that point. Since the game is shot in shooting positions of no more than 8 shots per position or view, even a single stack .45 1911 has 8+1 rounds, so there will still be the last round in the chamber when the person hits their reload. And in the other divisions, the guns can have much higher capacity, some up to 27-28 rounds, so there would be no reason unless someone has really screwed up that the gun would ever be empty.
It is not only common to not shoot the gun empty, but also to modify guns so that they don't lock back when empty. The reason for this is to avoid the possible reliability issues that come from the lock back function (e.g., I just got a new 2011 that likes to lock back with 1 round left in the magazine, so I will be installing followers without the lock back function when I get around to tuning the magazines to make them work).