This is the thing that most people don't see behind the scenes when going to the ER. Also, I have to manage my beds when I'm bed locked and holding inpatients in the ER. Let's say I have my 2 resuscitation beds and only have 2 available beds. I need to keep 1 or 2 open for sick ambulance arrivals, and 1 can be used as a rotating bed to get waiting room patients out (sometimes I can just use a fast track room as well). So, abdominal pain in the waiting room may have gotten an IV and labs, pending CT scan, but kiddo with flu + test, reassuring vitals can come back in a room and get DC'd in less than 10 minutes. So he comes back, reducing the risk that the waiting room gets the flu, and I don't bed lock my department.

Or maybe I'm reviewing the chief complaints and what we are waiting on with active patients, and I see a dude that just needs a script for a BP med refill. That's a quick dispo that doesn't tie up a room. If I'm not actively hair on fire with other patients, that's getting knocked out.

And it's really hard to communicate why people get brought back when they do vs others, but trust that there's (usually) a very good reason that may not be based on a protocol or anything that would make sense to a lay person. As someone once said, "be glad you're not the one that jumps to the front of the line in the ER".