I would say a BUG is only necessary if you feel better about having one.
Personally for me,one gun is enough for my needs.
Right. As long as you leave out the unforseen reasons why a BUG might save your life, then a BUG isn't necessary.
Interesting logic that could apply to the primary gun as well.
I carry a J-frame in my inside vest pocket--sometimes in a pants pocket. I can secure my primary weapon in the car and not be unarmed at Dr. appointments, etc.
With a BUG, I can arm a competent person if necessary.
In the Winter when it's cold, the coat is zipped up restricting access to my primary, the J-frame (or LCR) is in my right coat pocket---where my hand is.
Not meaning to pick on you personally, but your logic is widespread and your statement speaks for a lot of people who have the averages all figured out.
The number of shots fired in gunfights, the % of the time one needs to reload, that they don't live in a bad neighborhood (what could go wrong there?), etc., etc.
Without considering that averages include the extremes, they're equipped for the "average" deadly encounter.
Just my thoughts on the matter.