Many governments in the past have taxed their civilians, and for a very good reason. Financially, a country/civilization cannot function without financial backing. The government obtains this from their residents. And the tax money supports government operated facilities, such as the police department, the fire department, roads, military, etc. By living under the government, in exchange for the services that you cannot pay yourself, you pay taxes. If the government stopped taxing everybody, debt would skyrocket, municipal services would stop, and the countries military would no longer be able to function because the government cannot fund these anymore. And, the municipal services that the government provides us create thousands upon thousands of jobs for people.
Also, taxation can dissuade people from purchasing certain products, such as goods from outside the country, or items that can harm the user, such as alcohol and tobacco products.