Uncertainty has a lot to do with it. There are proposals out there that would tax ammo, some proposals about guns that may or may not include the "lowly" .22. If I crank my tinfoil hat down good and snug, I can tell you why I'd want 20K of .22: barter. Now we don't do TEOTWAWKI threads, but I can imagine several scenarios in which I'd want enough .22 to both: (1) take down small game; and (2) trade for other supplies.
A gunfight is not the time to learn new skills.
If you ever have a real need for more than a couple of magazines, your problem is not a shortage of magazines. It's a shortage of people on your side of the argument. -- Art Eatman