Have you ever seen the "share a seat, win a friend" sign? I have yet to meet a person who actually won a friend just by sharing his extra seat.
I don't know who coined that phrase, but i do know it wasn't really meant to encourage camaraderie and friendship. It is a device to accommodate people in scrumpy places.
We all know why those signs are there. We don't believe it - but we still do what it says. We still share that extra seat out.
I don't know why, but it is probably because we have this hidden faith, even with just the slightest possibility, that we might just win that friend, indeed!
It's like that feeling we get before opening a bag of Chickadee's -- we anticipate that free toy; in the same way that we anticipate winning that free "friend."