As with all real forces within our world, magic must abide by the rules in which our world is comprised. Magic has the potential to do anything; it will never be able to do everything. And even if it could, why would we want it to? The kind of destructive nature magic of that magnitude could have in the wrong hooves would be apocalyptic.

This is why we have hospitals. This is why we still have to grow food. This is why houses take more than a day to build and why death is still a threat.

Fantasy and magic are two different things, but it seems like sometimes ponies forget that.