I could see carrying a back-up gun if someone works in a profession where they have the responsibility to protect people or confront criminals.
Not picking on you personally, but your post is a good example of how lots of folks feel.
I carry a spare 642 most of the time. I don't arm myself differently on a day to day basis according to what neighborhood I'm going to visit.
The spare is for emergencies and, yes, peace of mind which is a big part of CCW even if you have just one gun.
I can use it to arm someone I trust.
If my primary weapon is unaccessable or out of commision, I still have a gun, and when I visit the Dr., Dentist, etc. I still have my S&W 642 in a vest or pants pocket. I'm not disarmed while my primary weapon and gear is secured in my car.
In the car, it can be placed between the console and passenger seat and is quickly available, since reaching for my primary weapon carried at 4:00 can be slow.
And, in the winter when I'm out all bundled up, it goes in my heavy coat pocket--same as where my hand is.
Saying "I don't need to be armed", or "I don't need a spare gun" is like saying "I don't need a fire extinguisher". Not really something you know until you really need it.
What you really mean is that "the odds are I won't need it, and I'll take the chance". Your call. My BUG is too dang handy not to have with me.
Just my thoughts on the matter.