For years I was a volunteer RO at my large private gun club. That behavior was totally wrong and very rude.
Protocols is to ask, or if the shooter finishes up and leaves its fair to pick up. Heck it just saves us getting a rake and policing up.
With that said as I help out many shooters with their problems, many would say do you want my brass. Range at that point was open to allow non member a few weekends to sight in their deer rifles. They had policed it and normally put back in a box. I took any reloadable ammo offered as if I did not shoot it became trading stock.
We had couple rather rich skeet shooters that bought their ammo in pallet lots at a very good price, they bought seconds that said not reloadable(but 90% was perfect, as I grabbed plenty). They did not reload but any that followed then could have their brass.