He couldn't hack driving a cab in Boston
... "Cab Ten-Twenty-One, do you know where you are? The customer is waiting!"
This must be 1021's first night on the job. After getting hired, all newbies are supposed to ride around with an experienced driver for a couple nights in order to learn the ropes. But it seems 1021 either lied, telling the owner he already had experience, or that somehow he fell through the cracks and was inadvertently sent out onto the streets cold. That or he is just a really, really slow learner.
"Cab Ten-Twenty-One, do you have a GPS?... Yes? Well, USE IT!" ...