Because TGS use to be bigger and more important than it currently is. Expecting that a SCEJ developed title might be making a reveal at TGS of all places is less moronic than it is you being condescending and presumptuous to think it such.
The Last Guardian originally debuted at E3, but it got a second trailer at TGS09 mind you. Expecting even an announcement, or something, is hardly moronic.
No, I think it very much is. Expecting it at this TGS, two months before launch, three months removed from E3 where SCE only bothered displaying one new big title in The Order shows a silly expectation. Call it condescending, but what am I to say to someone to who thinks TLG, the game that has become a become the butt of the joke in Western Media and has a heavy amount of attention on it, will be revealed again at a show targeted at Japanese gamers and is about the PS4 launch? It's even more moronic when you're pointing at me, and I told you it would be surprising to see that kind of title being revealed at a show like TGS of all places.
Also, key words in the bold there, it initially made its debut at E3. Not at TGS. Why the hell would you be dumb enough to expect it show up once more at TGS for it's re-unveiling when its been years since it was last shown, and people are obviously very curious about what's going on with it?
By the way, the last few SCEJ titles like Puppeteer, Knack, GT6 and Rain made their debut on a show/event which wasn't TGS. Crazy, I know.