Ideally, the first group in the door does that check, as they're the ones with the luxury of more time, with the door open while waiting for the green light. But too many people don't do that any more... Even if the first group fails to do so, it only takes a couple of seconds for the next guy up to the door to sweep their eyes around, while they're doing their count waiting to exit next. If you're on jump run at 13,500', and you want to scan an area of two miles radius, that's less than a 45 degree downward angle. So, you're not really looking that far outward. Look down at the floor right now where you're sitting, and sweep your head so that you scan a 45-degree circle. Didn't take long, did it? If there was a bug crawling across the floor in that scan, I'll bet you would have seen it. And the human eye is naturally attracted to movement. If something is out there, your eyes should zoom in on it automagically. You can't stop this from happening if you try - it's a hard-wired survival instinct that's probably millions of years old. Those that didn't have it, got eaten by saber-tooth tigers, and fulfilled Darwin's theory.