I am still new to this but it seems like at the start of the match everyone helps pick up brass/reset and then towards the end every stops.
If you don't have time to pick up my brass im not picking it up for you. Or if it isn't important enough to you to pick up yourself.
The range i shoot at has a policy that you police your own brass so no one has to pick up after you, i see it as a polite thing to do