It’s a sad reality of mainstream cinema that most audience members need to have the story spoon-fed to them. The answers have to be spelt out clearly, and they’ll get angry if a plot point is kept vague or – heaven forbid – they have to decide for themselves.
If test audiences are confused by a movie, the studio will probably retool it, making sure to remove any lingering mystery. However, some fans love the chance to decide for themselves. Questions like whether Cobb was really dreaming at the end of Inception, or just what the hell was going on during The Shining generates healthy debate among movie nerds. It’s more fun to speculate than get a clear answer, though sometimes the answer has been there the whole time.
Maybe the filmmakers reveal its years after the fact or a novelisation explained what the movie kept vague. Sometimes the discussion can continue even after the fans know the answer, but for the smug out there it can be satisfying to know they guessed it right.