Distance is a tactical advantage when faced with an adversary. Distance gives you time and is your best friend when confronted with unlawful conduct.
The myth used to be that 21 feet was a safe distance. But studies and the now famous Tueller Drill, have proven that unless you have your hand on your firearm, or it is out of the holster, you stand a good chance of getting injured and never getting a defensive shot off.
An assailant can cover 21 feet in 1.5 seconds. For most police officers and a majority of carry permit holders you won’t be able to get your sidearm unholstered nor will you be able to get a shot off.