blamecharles
Master
In my experience, it's definitely 9mm in centerfire. Just look at the floor of any public range you go to. It's .22 and 9mm brass all over the place. Some may be the delusion that picking up 9mm brass to reload isn't worth the time. I'd wager it's simply the sheer number of folks who shoot those calibers myself...
When i sweep up my brass i take everything in the pan, it all goes with me even steel case. At home it gets separated and stored, Never know what SHTF may bring.