Agreed. A problem you may run into, in practice, are the people who will tell you its not essential when the (voluntary) collection hat comes around, but then use the service anyway (for example a road or public park). So there will need to be a mechanism to prevent such people from using any services they voluntarily chose not to support. But then one begins to wonder if a mechanism like that, if it is robust enough to prevent people from driving down certain roads or admiring the nicely groomed park, is not just another government by a different name. No?