Big Brother could care less about the tax. They already get money through the gas tax. It's mainly a way for them to track our every move and then punish certain driving and other behaviors with increased taxes and fines, or even criminal prosecution.
The government will use it to monitor our commute habits, driving speed, parking locations, meetings we attend, who our friends our, what bar we attend, etc, etc.
It is one of the most significant threats to freedom ever proposed in this country and must be fought tooth and nail.
Our ancestors really let us down when, in the name of public safety, relegated a "right" to travel on publicly funded roads to a "privilege" to travel on publicly funded roads.
Driver's license requirements, mandatory insurance, blood alcohol content, check points by police, all have quietly and effectively diminished a right so it was only a matter of time before the state wishes to monitor your every move for the sake of revenue or any other reason.
Again, that is what happens when rights become privileges.