Is that a good comparison? How often does the average person actually see either of those things? The reason it's surprising that people struggle to draw bikes from memory is that most of us see them all the time.
How a bike fits together it's kind of irrelevant for most people, even if you ride one or if you must dodge one.
A caricature is one thing, and might be doable by an average person, but knowing how to do a caricature is a skill all by itself. A portrait is extremely art skill intensive.