We pay taxes simply because it can help boost the economy, gather funds to build public office, buildings, establishments. It also serves as government funds that intended only for government used such as projects that helpful for the people. Paying taxes is required by the law and are abide to pay for it if not then you liable to be sanctioned by the government.
These are only taxes that run the economy of a country. Taxes are the only source of income for the government. They have no other high sources for making money. All the government employee salaries, big projects, health and education facilities provided by the government is due to our taxes. Without taxes government can do nothing for their people.