Why or why not? Weight, ammo difference, having to dress for two guns not just one, double the chances of printing, etc, etc.
Look, if you take the extremist view of guns reliability, technically you have to buy a new gun, shoot it to destruction, buy another one, rinse, repeat, repeat, repeat, etc. It's a point of view that tacitly admits you don't have confidence in the pistol you picked to carry.
Myself, I picked the pistols I have the most confidence in and have done enough testing with them to give me confidence that if I have to use them they will go bang and hit what I am aiming at. Could they still fail? Yes. But I have done everything reasonable to ensure that they won't fail. All you can do is all you can do. At some point you have to take the field with the one you have the most confidence in, and work it from there.
Do as you wish. But you couldn't be more wrong about the rest of it.
Mechanical objects fail. Period. Nothing extremist about it.
Matter of fact, I could say that you are ill prepared to go out in public. How do you like that? Don't call me an extremist.