Even if that were the true motivation (which I don't believe), there's a standard UI paradigm for that: grey out the control if it doesn't apply. I'm more incl

Even if that were the true motivation (which I don't believe), there's a standard UI paradigm for that: grey out the control if it doesn't apply. I'm more inclined to believe that it was a UX designer with a misplaced drive to simplify at all costs.