Tanenbaum may well have not been using an analogy. He might have been talking from personal experience.
I have a co-worker whose father worked in the Bay area during the 70's and 80's. Back then computer time was expensive and not many places could afford to install high quality hardware (basically the 70's mainframe is the 2010's data center - there are relatively few). So people who wanted work done would have to ship their tapes over to the computer and have their job run. My friend's father was one of these couriers who would run the tapes around in the back of his station wagon.
My grandma tells a story about when her husband and her brother were running an experiment in grad school that needed computer analysis in the middle to tweak the final run. The problem was that their lab was on one side of Oakland, and the only computer they had access to was a mainframe on the other side of the city. And they only had the lab for one night.
So that night they had Grandma sit outside the lab in her car. As soon as their first run was done, they ran the punch cards with the results out to her. She drove across the city and started the computer run while they reset the experiment. As soon as the run finished, she drove the new cards back to them.
They ran their second experiment, got their results, and got the best grade in their class.
The way Grandma tells it is that she was driving 90mph across the city in her brother's Corvette at 3am. I'm not sure how true that part is...
I have a co-worker whose father worked in the Bay area during the 70's and 80's. Back then computer time was expensive and not many places could afford to install high quality hardware (basically the 70's mainframe is the 2010's data center - there are relatively few). So people who wanted work done would have to ship their tapes over to the computer and have their job run. My friend's father was one of these couriers who would run the tapes around in the back of his station wagon.