Hmm, that's an interesting question - if you're unable to be fired, do you still have a moral obligation to do your job?
Well, I'd say yes.
I share your opinion and bankers abuse it.
I'll look for the definition of moral obligation for politicians. Hoping that there is one.
But still - ceteris paribus, which politician will win? The one slightly more upstanding, or the one slightly more charismatic? There's a strong selection pressure in democracy that favors populism and short-sightedness.