Because the showrunners are more evil than that sneaky smoke monster, they feel the need to continue to torture audiences by refusing to explain what the hell is going on at that effing island until the very last minute, and have yet to reveal one final scene that not even the actors know about.
According to Desmond, aka Henry Ian Cusick:
"All the actors have the scripts that goes up to the tenth act of the finale. [But] no actor has the eleventh act, to my knowledge. So we don't know what's happening in the final act, which I think we're gonna film soon. I've heard that even with the final act, there's a missing scene!"
Maybe they haven't revealed it yet because the writers are still trying to figure how the eff they're going to explain all the crazy they've been spitting out for the past six years!
We hope not! We know people who are going to lose their MINDS if they don't get a satisfying conclusion to the series!
The pressure is on!!
What do U think, Losties?? What happens in the missing scene??