For many, it's a morality, not just an expectation. You're a
bad person if you're not mediocre. See this from a recently posted article 6 hours ago:
> It does preclude, practically from first principles, those exceptional individuals many of us have encountered in our career who seemed to be able to hold the entire code base in their brains. Arguably that’s a net positive. Those individuals were always problematic similar to those folks who are willing to work 80 hours a week and jump on every incident. At a minimum they make the rest of us look bad.
Not only is working too much bad, but competence and intelligence itself is bad, or at least suspect. No doubt it's rationalized as being against anti-teamwork traits, but the reality is much more sinister -- jealousy, and lies to package up that jealousy as something that isn't jealousy.