I am really, really, really tired of law professors complaining about rule X on the grounds that it’s “underinclusive” or “overinclusive” or both. These arguments are typically followed by whatever is the printed-page equivalent of sitting back in one’s chair with a self-satisfied smirk.
So the rule you hate is underinclusive? So what? Most rules are. Your proposed alternative probably has exactly the same problems. All of life is underinclusive, and overinclusive, too.