The obvious question! Because taxing is used to free up the resources necessary for the state to purchase them. Once you force everyone to pay taxes, they have

The obvious question! Because taxing is used to free up the resources necessary for the state to purchase them. Once you force everyone to pay taxes, they have to get hold of the state currency, which should (in a well managed system) only happen through state purchase of resources, notably people's time. That is, the ability of a state to provision itself is driven through its currency which in turn is driven through taxation.