Thing is, every time I've gone to my local indoor range, nobody....and I mean nobody ever picks up brass.
If I find out where this range is located, they are going to have very clean floors after I visit!.
My Club range is frequented by very experienced shooters. The only brass you see on the ground is rimfire and steel cases. Boxer primed brass cases are hard to find.
The Bullseye shooter cartoon is only a little exaggerated. Competitive shooters are brass fiends. A bud of mine was shooting service rifle back when they issued you ammunition. The stuff back then was 308 LC match, the good stuff. He told me of his frustration of finishing his string, and in that period when the range is cleared and before he could get his equipment off the line, people would run out ahead of his position and scarf up his brass.
Go the CMP Garand match at Camp Perry where you fire issue ammo, and you will see those brass fiends in action. It is like a feeding frenzy for sharks.