People who recommend stocking up on ammo - what are you planning for?

I hear food, water, ammo constantly from preppers. Food, water yes, bullets, enough to kill some food with makes sense, but stock piling ammunition? Do you think this is going to turn into a video game where you sit on your porch as a never ending onslaught of zombies tries to take control of your front porch?

Seriously guys, when you start talking about having a mega ammo cache you're worse than Rumsfeld in the burbs with the walkie talky up on his roof. (https://www.youtube.com/watch?v=_wnldWZ_BEI)

I grew up hunting, I take great joy in shooting, especially at long ranges. That being said, if things were to get bad enough where I have to on a regular basis, threaten to take, or actually take human lives with a gun, I'll only need 1 bullet at that point and that will be to extinguish myself because I'd rather not be around to see it.

So yea, I think someone with 20 different guns and ammo cache is fucking nuts, but hey that's just me.