wot's a title?
The politicians are responsible for making laws that govern the country - the police for enforcing them.
The two houses of parliament are there to balance each other - one is elected and changes form on a regular basis, whereas the other is composed of people who are regarded as having contributed to the good of the country and are deemed to be working to the best interests of the country, not folding to whatever political pressure is paramount at the time.
It's all a system of check and balances, and Ok it doesn't work perfectly all the time, but welcome to the real world. Anything that has people involved will be succeptable to human interests - the best that can be done is to ensure that there are non-interested parties performing an over-sight function, with the power to intervene if the situation calls for it,
Why is it that the politicians feel that the police force would be better off having voted-in chief constables, rather than ones who have worked their way up through the ranks and know what the job entails?
Silly politicians - leave the police to manage their own hierarchy, unless you would want the police to decide who can stand as an MP? no - thought not....