The real truth is something in between. In local and smaller matches, I usually head home with most of my brass. When at larger matches, I am lucky to head home with 50% of my brass. And I try to pay attention and be there when brass is thrown on the table at the end of the day. And I try to pick up my brass right after shooting a stage, when possible. But there are often so many stages with movement and barricades like rocks and things where policing my brass is not possible after shooting the stage.
I see people post up all the time that they end up with 95% of their brass on average and just do not know how they accomplish that without catching it as it is ejected (not very practical or realistic for these matches).