If some guy walks into your government office and says he'll give you ten million dollars to increase everyones' salaries, but only if you arrest all the homeless people on his street, you just created a perverse incentive. You can claim that anti-bribery laws fix this, but it's a who watches the watcher problem. To be clear, regular government has this problem too in the form of political donations and lobbying, but removing even the thin veneer of legitimacy that our current taxation system has (where you can't opt out of paying for social safety nets or into specific initiatives) makes open bribery almost inevitable.
