They had a PS Meeting and E3 in 2013 just fine.
Eh, it being fine then doesn't mean they have to do that same thing now. Let's consider a few things:
-Sony likes the exclusiveness of having their own reveal event such as the PS meeting. They like having the spotlight and having their own event means they don't have to share it.
-They like the spectacle of E3 press conferences and the way it hypes up the player base and potential buyers.
-You say what they did in 2013 worked fine, but the majority of people in gaming forums are saying that Sony won at that time only because "MS dropped the ball." (And I think there's a small amount of truth to that. I think they announced the PS meeting out of nowhere to catch MS off guard (specially their marketing arm), they stuck the sword on the ground pointing up and just let MS ungracefully fall on it themselves. I don't think that'll work this time around, MS is much more prepared.)
- A while back, Someone high up from PS (House?) said that many people didn't like how they revealed the console but didn't show the hardware, I think they're going to avoid doing that again.
-That year's E3 was mostly just a rehash of the PS meeting. The feeling of dissatisfaction thats going around online concerning their conferences lately, I don't think they want to do that again.
-Kodera's comments of 'crouching before jumping.
Let's combine these things and Sony's plans become a bit more clear. IMO, they want an E3 sized event, at the time of their own choosing, where they can show fresh and exciting games, from first, second and third parties, coming in the next gen launch window and beyond. They want to be the center of attention. They want to show off the console specs and the console itself at this event/conference. They probably even want it to be like PSX and have the console itself on the show floor, for the press and PS fans, with demos of launch games. They want to have a launch date ready for this event, and they want to have clear on concise plans ready to be shown.
Idk about you guys, but an event like that would blow my mind.
Ps. I don't think Sony is leaving E3 entirely, they'll be back next year... it just doesn't fit into their next gen reveal plans this year.