2 is a good question. One answer is presumably mandatory payments for social security and health insurance. You can't spend money recklessly anymore that you gave to the taxman.
On the other hand, if you can't save money, spending it recklessly is much more likely. Politicians who choose not to spend money now cannot expect to choose to spend it later (due to the uncertainty of being reelected), which creates a strong incentive to just spend it. It would be a rare politician who could be elected repeatedly while running on a policy of saving money for the next generation's government to spend.