What part of the human psyche makes people have to out-do one another, even when they're total strangers?

I was having a conversation in the lift with an acquaintance just now and a complete stranger felt the need to interject that he starts at 7am, and 'beat that'. No, seriously - I have no empathy for you. I have never seen you before in my life and probably won't see you again for at least a year in the lift. WHY would I want to beat that and why do I even care that you start at 7am? That makes you a twat, and me not.

arghhhhhhhhhhhh!

Please one-up me with your examples now.