I personally like the explanation above provided by @DEFCON 1 , and that is how I would explain it via the in world fiction.
That said, from a mechanical perspective, I feel like this question has been brought about by recent changes MTOM; which seem to have been a reaction on the dev's part to their sloppy design with counterspell (anti-magic zones have always been in a weird space but come up less frequently), despite how (in)frequently this comes up.
That said, from a mechanical perspective, I feel like this question has been brought about by recent changes MTOM; which seem to have been a reaction on the dev's part to their sloppy design with counterspell (anti-magic zones have always been in a weird space but come up less frequently), despite how (in)frequently this comes up.