If the toll is voluntary, I don't have to pay it, and never will.  Way would anyone pay the toll if it's voluntary?

Shall we try an experiment?  Go get a job, but tell your boss that paying you is voluntary.  I bet you'll have a million employers willing to higher you, that will choose to not pay you. 

If you're going to say that I can't use the highway unless I pay the toll, well, that's not voluntary then, is it?