Same as for any automated system: reliability and throughput.<p>Some of these airports are enormous, Schipol especially so. They&#x27;re handling 150,000 bags per day at peak times. If you generously assume a 1% error rate (<a href="http:&#x2F;&#x2F;panko.shidler.hawaii.edu&#x2F;HumanErr&#x2F;Basic.htm" rel="nofollow">http:&#x2F;&#x2F;panko.shidler.hawaii.edu&#x2F;HumanErr&#x2F;Basic.htm</a>) and that each bag is touched by only one human, then you&#x27;d be misrouting or losing 1500 bags per day, which is huge. But of course bags aren&#x27;t going to be handled by just one human, there would be many making complex routing decisions, over and over again. So the true loss rate would be much worse.<p>Bear in mind that if the airline doesn&#x27;t get the bag to the right place then the bag has to be sent onwards later, and then the airline has to pay for home delivery of the baggage. So the cost of mistakes adds up fast. Then you have the sheer amount of manpower needed to move all the bags around by hand. And not just any manpower, it often has to be <i>literally</i> manpower because you need strong men to do this as the bags are so heavy, and they can&#x27;t work long shifts because they get tired.<p>It&#x27;s pretty easy to see how such things can be justified. You wouldn&#x27;t be able to scale air travel to the current levels it sees without such systems.