Sometimes that's all someone can carry, for a variety of reasons. Before concealed carry was passed in Texas that was all I felt comfortable carrying on my person, a tiny-go-everywhere-nobody-sees-it Beretta 950 BS .25 ACP. After concealed carry I worried a lot less about someone seeing my gun by accident so I switched to J frames and as my comfort level grew I switched to snubby K frames and compact .45s or 9mms.

But I still keep mouseguns around for those times when I will be somewhere and what I will be wearing dictates invisibility over caliber.

Surviving an armed ambush, the main topic, is usually a matter of pure luck. No matter how much training you have, gun fighting skills and hand to hand fighting skills, if you can't see it coming you are in deep kimchee from the get go.