People can do what they feel comfortable with, but I always carry an extra mag if I an carrying an autoloader. If only for a malfunction. Twice in my career my partner at the time had their magazine come out of their service weapon. Both occurred on gun runs. Both times they instantly replaced the magazines and carried on. Two different partners 2 years apart. Both while bailing from the cruiser. While I was a firearms instructor for the same agency I witnessed many a time magazine failures from falling out of the gun, improper re-assembly or factory defect. An extra magazine gives me an option, however unlikely i may need it. Just my .02$