Backwards logic. If someone has no money but has power, they can sell it for money. Which they will be more vulnerable to doing, if they are on a very low salary for the stress levels and responsibility. If instead they are NOT thinking about their bank balance, and some other metrics for recruitment are put in place to psychometrically-test for bad characteristics (good luck with that, this is politicians we're talking about!) then they can be free to vote as per their conscience. That's the theory, anyway...