I think it is just because the way it looks when all zipped up, it can look very collapsable. So they just don't bother with it.

Some subtle positives

-It has handles everywhere for easy carrying. You can make it a backpack, or hide all of that and just carry it like a duffel bag.
-I walked in downpouring rain in Rome for quite a while and none of my electronics stored in the daypack got wet (the daypack was attached to the big pack at the time). So I consider it "pretty waterproof" for electronics
-Notice how the bag hides all of the zippers well (for security?). It looks clean..

Downsides

-There seem to be a lot of straps. Just tons of straps for various things. If you plan to load it up - with sleeping bags, sleeping pads, and etc. This serves you well. But otherwise you are left wondering what all the extra material/straps are for. I was slightly annoyed with it.