As TIbfox mentioned the same thing about low salaries, I do understand that... But nobody forces you to accept the job if you can't do it... It's hard when you have no job, but still, even if I do it for pennies or nothing, I will do my best to do my job well...
But this is not just the delivery guy issue... Big companies do whatever they can to get as much profit as possible, even if that means low customer ratings...