David Smith in a post on his blog:
I have just sorted through the App Store and settled on trying out your app. I open it up and you immediately ask if you can send me Push Notifications? I have no context about what these are going to be used for or why they might be useful to me.
I haven’t even seen your app yet!
I agree with Smith's sentiments. The marketing angle is something that Apple has not specifically enforced, but one never knows how the app review winds will blow.
Unfortunately, Apple's own documentation for remote push notifications (specifically, the code sample) implies that a developer should immediately register for remote push notifications once an app has launched. I can only imagine that the lack of clear direction from Apple must be a significant factor in the way apps request permission for push notifications.