In the world outside of stack ranking, you aren't winning/losing against your peers, you are being paid what you are worth. Backstabbing somebody else does not change your worth, it just makes them less valuable than you. So your salary does not change, theirs just goes down.

Far more importantly, I have spent my 25 year career in non-stack ranked companies, and I have never seen the behavior you describe. Yet just about everyone at stack ranked companies report back stabbing behavior. I think empiricism wins over speculation.