Because everyone knows the private sector is always more greedy, power hungry and corrupt than the public sector and competition has no tempering effect on it. Only the government, without competition, can be reliable, capable and responsible. You don't really believe that, do you?
The government is supposed to be above that and be working for us not on us.
It never seems to work out that way though. It's usually the government that's screwing us and private industry who's working hard to earn our business. You have it all backwards. Whenever the profit incentive is missing, the probability that people's wants and needs can be safely ignored is the greatest. If you took a poll asking people which services they are most satisfied with and which they are most dissatisfied with, for-profit corporations would be located at the top while non-profit organizations would dominate the bottom.