Various situations call for various applications. A sidearm has some accuracy up to maybe 25 feet. After that something else would be better, and notice that the mobs operate as mobs, so 15 rounds will buy you a few seconds before you have to go to Plan B.
Additionally, all of these mob attacks are at very close range, and I want something really comfortable in my hand when it occurs. And usually, after the first shot, most of the mob starts running, especially the more “tribal” in nature mobs.
plan b is machete and knife