Page 42, applied judiciously.
Magic is the effects of a Magical World that can't be described through Mundane means. The D&D games we play are in magical worlds, and "A Wizard Did It" moment will occur because of that.
Come and Get it can be explained in the majority of cases in rational causes, if desired. If you run into a corner-case, your choices are to reduce some aspect of its use into "A Wizard Did It", or do deny the action under DM Fiat.
That said, we're thinking far too hard about fantasy here. Dragons can fly in an anti-magic field, to quote a recent OotS strip! In any Magical World, there are things that can't be simplified as mundane or it wouldn't be a Magical World. At some point, "A Wizard Did It"; and this is a great place to be.