Re: Someone please explain why....
I think essentially, the idea is to spark the age old philosophical question of "what is real?" How do we know life isn't all a dream? Etc. He cuts before we actually get to see the top fall, which would give us closure, instead opting to "incept" the audience with a lingering question. Or perhaps encourage them to take a "leap of faith". If he didn't show a wobble, then it would strongly imply that Cobb was still dreaming. This way, it can be taken either way. That's why I think it's a pretty genius ending. By simply cutting it a few milliseconds earlier he created an entirely different effect. The audience I saw it with erupted with "No!" and "Awwww!" when it cut to black. Wouldn't have happened if the top fell over and we saw and heard it hit the table.
I'm with you though, I believe Cobb is in reality. But I've seen some convincing arguments for the contrary, that's all. Whereas with TDKR I find the "Bruce really died" arguments to be completely stretching it and going against the point of the movie. Unlike Inception, where the ambiguity went hand in hand with the point of the movie.
^ And that right there, is me trying desperately to seem like I'm still on topic. lol