Amen!If.
Maybe.
Probably.
Having loaded mags means you can return more sustained fire in a given period of time.
Might you be overrun by "zombies"? Maybe. But I am betting that if that happens, I won't be saying "gee, I have too many guns, mags and ammo - I wish I had spent that money on a vacation instead".
If I am besieged by gov forces - yes, probably not going to make a difference. In which case, so what?
There have been times when I have said "I wish I had bought more of these mags or ammo when I could", but never the opposite. I hope I never have to use them in a firefight, but if I do I am not going to regret having too many guns, mags or ammo.
YMMV