Hmm... It is, for the most part, unnecessary. I do see one upside, though. In this scenario, the game should get automatically downloaded to your system, when the time comes, so that you can start playing it. That's about the only good reason behind it.
But, I don't preorder digital games.

Also, I'll take physical over digital whenever I can.

i'd rather own the disc so i can sell it when i'm done.