For some goods it is impossible to charge for them in the conventional sense. Private goods are goods which firms can restrict to those who pay for them. Once the good has been bought, the person can then consume it themselves and get the benefits from consumption.
Public goods are different in nature.
It is also true that one person individually being defended does not reduce the amount others are being defended, also making the good non-rival in consumption. In contrast, a private good like a Mars bar is rival in consumption. The only way to provide goods of this nature is therefore through taxation. This is where your taxes come in.