Coach Guns.
Proven history of being reliable. These are not dependent on ammo to cycle an action. Safe, as mentioned can be left loaded with hammers down. Fast to action akin to why Double Guns are used to hunt Dangerous Game. It needs to be in use, fast, quick to shoulder and get on target. With a little practice, firing two, ejecting spent shells and shoving in two more, as Dangerous Game hunters do, enable 4 fast shots.
Easy to hold one handed on a BG, if need , while dialing a phone for Police, Sheriff, EMT - whatever.
We really do have folks do this holding a BG at bay with shotgun one-handed and having to use phone drill Some of these shotguns with mag extensions, side saddles and all - get heavy. Remember most / some of us set up home guns for the smallest person in home that might have to use it. 12# shotgun, for a 15 y/o petite teenage daughter, kinda tough, now a 6 -6.5 # 20 ga coach gun, works right well.
Not only more PC, also more PC and easy to break down when traveling. Yes, some known trainers carry a Coach gun in traveling. If the Jurisdiction says "no", very easy to break down and be legal while driving through.
Versatile. Darn things tote so well just walking the property. Reload lighter loads if need for teaching new folks, and work up from there. CAS of course, still toting one for bird, small game is ...it just feel good, and one feels good about toting one.
Some of the same reasons I still like a single shot shotgun in 20, 28 and .410.
In fact near me is a single shot youth model in 20 ga, what I keep handy for the house.