I understand you, but think about it this way. Most of the time when leaks happen, they tend to spawn new threads, news and headlines all over gaf and the web. Only seeing minor info like "new bend game sci-fi" or "sonys megaton revealed" is really enough to dampen the hype and excitement for the real show at e3.
Even more, c'mon this is gaf, we all share our enjoyment together, we talk about games, our joy, our hate all together. You have to admit, that when leaks happen and some part gets to know about them beforehand, the reactions & responses at the official reveal is totally different and boring. No emotions, just "meh", "this looked more like xy-game, what happened?" and so on.
We're in this ride togther. Curiousity is in all of us, so it's absolutely fine for wanting all the leaks. But just remember the last times when you were legit shocked at some of the reveals from the past. And now compare that to your feelings when you got the official reveal to a preveiously leaked and known game. It's night and day.
Wouldn't it have been so much more memorable getting the first scoop of project beast tomorrow? Now everyone already knows and only details will matter. A real shame.
But don't get me wrong, I am not 100% against all leaks. Like everything in life, the middle-way is the right way. I am totally for leaks like ms online/no used games plans, because this way we can ensure a medial riot so that plans against us get stopped in their tracks.
So yeah, game leaks are not beneficial imo.