I would just like to add that it is quite common at the airline and base that I work for, that even though a passenger checks in before the cut off time, and even though the bag successfully makes it into the hold, the passenger themselves doesn't get to the aircraft in time.
So, for security reasons, Loaders then have to get all the bags out of the hold and locate the bags associated with the missing passenger. Result? Delays at best, missed slot at worst.
My involvement in this process is strictly to get the aircraft moving with the minimum delay. Theres no point scoring - if the passenger turns up before the loaders find their bag, then they travel. If they find the bag first, we're gone...
And this is what happens when people check in
on time. If you're late, unless the terminal is very small and unbusy, you're on a no hoper.
CPB