Why do people make bets?

I am not thinking so much of casino gambling, which requires its own set of explanations. I am thinking more of things like betting on a team or any future event or even betting on the truth of some statement. I know the urge comes quite naturally. There have been times when I am arguing with someone and I get to the point where I will say, or am tempted to say, that I am willing to place a bet that what I am saying is true. Why do this? In my personal cases, it is certainly not motivated by risk taking or financial gain, although I can see how these can be a factor, but there must be something more.

There is something in the nature of betting that, if not inherently unethical or illegal, has the potential to turn into unethical or illegal behavior. Sports betting can lead to things like point shaving. If I placed a large enough bet that someone would die, wouldn’t this be very close to putting a contract out on someone’s life?