When things become automatic, they're inflexible. The meaning of a word comes for free after thousands and thousands of hours of staring at a squiggly line. So if we want to behave flexibly, we need noisier or more effortful control systems in the brain. And that experience of being in a situation that you're not prepared for is exactly the kind of plasticity inducing learning that will help your brain stay adaptable and plastic and flexible with your environment.