In movies, timing is everything. And we aren't just talking about pacing here. We're talking about heroes coming through in the clutch at the last possible moment. It's a trope that, when executed properly, is the most exciting and then immediately relieving moment in the entire film (see Boomer in Independence Day to understand what we mean).
Of course, in their respective universes, heroes are prone to being a little late, too, right? No one has perfect timing all the time. And sometimes, that can lead to some unfortunate consequences.