One answer to the question why anyone would need a high capacity magazine.
Not “a” high capacity mag, “several”.
Both my Kahr and my M&P Shield travel with at least one extra [full] mag.
Never leave home without extra mags.
Also, *never* keep your gun or the back up mags loaded with anything but the good self defense ammo (new stuff, not reloaded). FMJ only go in it at the range.
More like the answer to why anyone would need a drum or beltfed