But as a consumer, what the heck am I buying? I'm not buying a physical product, I'm buying a sequence of 0 and 1. It's a license to use said app. It's not the 90's anymore where you own a CD with your program and that is your product. I cannot re-sell the "used app" when I don't use it anymore.
So if I buy the 'license' to use your app, I'm gonna be real effin pissed if I can't use it on all my devices.
Actually tying your purchase to your Apple ID is much better for the dev, because only YOU can use it. A CD with software is much easier to share with your friends.