22LR can be good for self defense. My 1022 throws a lot of lead and with a 30 round mag it would kill on the first shot, but after getting 20 little slugs into a perp, he might decide to seek softer targets.
But then if reachin in the locker for a rifle, the 12gauge with 00 buck would be the first thing i grabbed.
I talked to a EMT a goodly time back about his experience in gunshot wounds. While you are correct that a .22 LR can be lethal in one shot. It doesn’t tend to do it in a very timely fashion. There’s usually a fairly lengthy bleed out before it is lethal. Hence if you need to drop a perp, it really isn’t an ideal choice of calibers. The interesting thing he mentioned was that .22s were really lethal in chest shots because they tended to pinball along inside the rib case doing some really nasty damage (as they tend to bounce off ribs rather than penetrate).