I'm going out on a limb here...
But, since we spend a bit of time pondering, reading and posting on these cases, perhaps we are taking a pragmatic view...or perhaps a "worst case" view.
We know what a well-placed handgun round can do, and while we hope that will be the effect on the BG, we have no way of knowing what ammo he is using, and (perhaps) we may expect the worst if we are hit.
At the very least, most of us have never been shot (and hope to keep it that way) and being shot is an unknown factor (to us).
I have read more than once that inner-city gang-bangers view being shot as a badge of honor. After being shot once or more (probably fairly ill-placed shots by their fellow losers) their air of invincibility is reinforced (remember these are young males who already possess that mindset to begin with)...
If I am ever in such an encounter, I hope that my adversary is over-confident, under-skilled and chooses his equipment (both handgun and ammo) poorly.
The only variables I can control are the ones that apply to me. I'm too small to fight, and too old and busted-up to run.
My common sense, choices in equipment, my diligence in practice, my commitment to attaining and maintaining a certain skill level...and most importantly, my avoidance of putting myself in places/situations that may turn ugly...
I am no longer a young pup, and I give thanks for the fact that I have lived this long. I would like to continue doing so a bit longer. Making it through the second 50 years should be easier in some regards and tougher in others.
Again...focus on the factors you can control.