How long ago was E3? Until yesterday, it was the day after I last did a laundry. And that's a hell of a long time. I sat there in the laundromat with my 3DS, looking at the 134 people I met at E3. I've not had a StreetPass notice since.
Ultimately, that's what E3 is about: the people who attend it. This excellent video by Collective Visual serves as the final recap to last month's expo, from the perspective of those who attended.
Why I go is to see the newest games, of course. Why I remember E3, any E3 is for the folks I see there, and only there, every year.