I can scarcely imagine a situation where I would ever need a back up gun. I freely admit that I am rarely in a "bad" area, but even so, I wouldn't be inclined to pack double, an extra magazine, maybe, but two guns, no way.
Of course, this is just me in my world, and I live quietly back in the sticks. I mean no criticism to those of you who want or feel the need to carry a BUG.
I carry a BUG so that I may have a handgun accessable to either hand.
Let's consider for a moment, you are out with your family. After a nice relaxing dinner meal you are holding your two year old in your arms because she is tired. Your "better half" has the 3 month old in her arms. Now Billy Badguy comes to you and demands your wallet. Remember, one hand is occupied with said two year old.
My solution, if I am in fear of my life or said two year old's life, not to mention the baby and spouse, allows me to grab a gun instead of a wallet. No, I'm not advocating shooting in every situation. This is just a possibility. What if you had your two year old on your "Strong Side" and only one gun? OOPS, we can't rewind the tape and start over, this is real life.
Another scenario: You are at the range and your "Primary" malfunctions. You need to drive to your Gunsmith to give him the gun so that it can be fixed. On your way home you have to stop at the "Stop and Rob" for a gallon of milk. While the BUG may not be your first choice as a carry gun it is good enough to get the job done if you do your part. If you didn't have your BUG your Gunsmith would've loaned you a real nice S&W 25-1 to go home with,
being that you are an off duty LEO.
Another scenario: Oftentimes in gunfights people shoot at their opponents gun. What if your adversary shoots your gun, rendering it inoperable. You now have a real nice Paperweight. Again, my solution allows me to stay in the fight. I hope to never need to use a gun again, but if I do I want to make sure I have enough to get me home safely.
Biker