the amount of brain effort to do this kind of job is close to 0. you need a bit of physical prowess, but this is easily attainable in a couple of week. since the job was basically the least complex job one can ever have, the pay was low. and it made sense back then: you want to move on to a better job/better pay/better conditions? get better qualifications, learn to do a different job etc. of course i can't comment on what happens at amazon, but these kinds of jobs are so easy to do that it's ridiculous they haven't been completely automated till now. i do wonder what will happen to all these people once automation is 100%.