Traditional depictions of magic would seem to require introducing complex ontologically fundamental entities: some magician or sorceress says the right words and performs some ritual, and some part of the universe obeys their will. But how does it know when to obey someone's will? The stated conditions for the effect are far too complex to be implemented by a simple arrangement of mechanistic laws, the complexity of magic must be at least that of minds. What seems to humans like a simple explanation, sometimes isn't at all.
In our own naturalistic, reductionist universe, there is always a simpler explanation. Any complicated thing that happens, happens because there is some physical mechanism behind it, even if you don't know the mechanism yourself (which is most of the time). There is no magic.