There's all these iconic photos of Walt Disney where he's pointing at stuff with a two finger point. I've heard that some within the company say that this is the example by which their resort employees always use the two finger point to direct guests.

In reality, he was holding a cigarette and the photos have been airbrushed. He died of lung cancer in 1966. Pointing with two fingers is just seen (kind of universally across cultures) as being non-accusatory. Like, say you saw someone talking to someone else and you cannot hear them (or it's in a language you don't understand); they're pointing with one finger in your direction, you may be inclined to think they're talking about you. If they're using the two finger point, you're less likely to think that... it's the same for airliner flight crew.