This actually differs from Nintendo's approach, as they still have a presence at the E3 show floor (& a large one at that). Sony is foregoing said show floor presence entirely if last year is any indication.
Remember when people said Nintendo was only abandoning E3 press conferences because they had nothing to show when they started doing the e3 directs instead, and now Sony is following suit in a far more drastic manner and nobody is saying Sony is doomed lol?
Compared to last year this is pretty obviously a "arrogant Sony move" but it's at least somewhat justified. Still, I wouldn't have seen the harm of even just having booth space there. E3 still attracts a lot of people in the general periphery of gaming.
So Sony Direct, Nintendo Direct and Xbox Playhouse are the remnants of E3?? Wow, Sony really making a statement. Your not bigger than the industry Sony, you can just release a video ala Direct and show up.