The way I imagined it, the maintainers wouldn't be considering a commit whose author was not willing to bet on its success.

This thought experiment took part in a world where the web was significantly worse than our own: hoards of malicious AI's and precious few humans trying to not be mistaken for a malicious AI. Of course a pre-existing trust relationship is much better, but ideally there'd be a way for untrusted authors to make it through to a real human somehow. Attaching money to the commit would be one way to do that.

However, your bet against it being merged incentivizes contrarian behavior by the maintainer in order to claim your wager for himself.

Similarly, betting that a public figure will still be alive a month from now is functionally equivalent to putting out a hit on him.