I have a couple. These days, I always wear one to a range where there are a lot of people, especially the indoor ranges. Unfortunately, all you need to understand why one is desirable, is to look around at the walls, ceiling, and dividers, and just stand back and watch the shooters themselves.
I also used to wear one for work during hunting season where I used to live, as I work outside and it was shotgun only. Its rifle where I live now, so a pistol vest is kind of pointless, unless you want it for warmth,(they do work well for keeping you warm) but there are a lot fewer hunters, and those that are around, arent near as knuckleheaded.