As well as reducing crucial steps and time in the defensive draw in a deadly force encounter, if you carry withOUT a round in the chamber, and your adversary is literally "on you" in whatever type of assault, God help you if you have to draw from concealment, attempt to rack your slide back AND fend off an assailant when both hands HAVE to be on your gun just to make it work.
It's unwise to enter any fight without use of your hands. Since an encounter within arms reach is not uncommon, speed means everything. In CQB, I encourage the good guy to use his/her non-firing hand to punch, jab, palm-heel strike and/or cover defensively while drawing and shooting from the hip with only the firing hand. This is impossible if your chamber is empty. You would be getting pummeled and likely never get the gun into battery.
Introducing an unloaded gun into such a violent encounter, when fractions of seconds and swift, decisive action separates first place from dead place, is futile in my opinion.