It seems like the best strategy because you figure other people know something you don't know. But since they always pick just one exit, that's not a valid conclusion.
Since the crowd behaves the same way whether they picked the best exit or a random one, you have no idea whether it's the best way out, but you do know it has added risk of delay and trampling.
Since the crowd behaves the same way whether they picked the best exit or a random one, you have no idea whether it's the best way out, but you do know it has added risk of delay and trampling.