To a character who is Literal Minded, a Cloudcuckoolander, or maybe just a little dim, or even a combination of all three, using analogies and figurative language is a bad idea. This is because in any given metaphor, there are several different things that a person can latch onto, but only one of these is intended to actually make the connected point. And unless the connection is made right away, everyone can end up discussing an entirely different tangent than what they were supposed to be discussing. Someone will eventually have to stop the new discussion in hope of returning to the original subject.