This is a do-over of an old YKTTW that I forgot about and eventually discarded. It's possible that a similar trope had been launched when I wasn't looking.
In a fantasy setting, artifical beings are often incapable of using magic. This primarily occurs in settings that combine magic and technology -- robots in particular almost never get to use the in-world magic equivalent, with creatures such as golems which are more explicity derived from Magitek having better odds (though not much better). The typical explanation for this is that you have to be "alive" to use magic; no matter how intelligent and humanlike an android may be, it will still lack that vital "something" required to rearrange matter with its thoughts. Alternately, it could be that robots simply cannot comprehend magic; try as they may, the concept of exploding somebody's head with one's mind is just too fantastic and illogical for them to truly grasp. The exact execution of this varies, ranging from being completely cut off from magic and immune to its effects to simply being incapable of using it. Video games often give robots a magic analogue, for the sake of balance. Please note that while the above write-up uses "magic" as the supernatural force in question, psychic powers frequently serve a similar role and robots are just as likely to be incapable of using them. Contrast Magic from Technology.