The screen might not be 100% necessary, but the buttons are. There was nothing quite like the experience of sitting down on the train, getting my Dragonfly Red plugged in, and having my ears blasted out while being a few taps on my phone screen away from being able to turn down volume
The A&K seems to lack buttons as well.
Though similarly, while I like the buttons and navigation on the W2 overall, I wish there was a way to not have to wake up the screen to change volume. For portability's sake, I totally appreciate that it effectively "locks" the volume with the screen off, but I don't need that feature when I'm listening on my couch. Maybe I'm missing something?