Differ if you must, but learning a new skill is not the same thing as learning to expand one's understanding. The latter is possible for everyone, the former is not (nor should it be). There's nothing wrong with not learning a new skill, and as brutal as we can be, there's nothing wrong with being a janitor. The OP, however, isn't about refusing to learn a new skill as much as it is about casually musing that those who do will be easily devalued by bosses for learning a "useless" skill.