The primary driver and motivation for politicians should be altruism, do good for the sake of it. So many people in NGOs etc. are capable of doing just that; working for "the good" even though it pays bad, why should we not expect that from politicians?
The US (I'm Swiss) is in my opinion a primary example on why you want to keep the kind of people that care about their own personal finances as far away from politics as possible. Let them play real estate sharks or monopoly at wall street or whatever floats their boat; just don't let them anywhere close to positions where decisions are made that impact not just their life but everyone else's too.