In part, the courts let them win. Why? So that the people have some good wins sometimes.
If the courts pressure people too hard, people will go out and look for relief from the courts. Then they will find the common law of the people (as distinguished from the common law of the courts).
The common law of the people can literally destroy government if government gets too oppressive. And it is the same for Canada, the UK, and Australia.
So, Government has to let the people win some of the time.
EDIT: The common law of the people can let you beat the IRS. Go to Craig Lynch's Youtube channel (
https://www.youtube.com/user/765736 ) and listen to all the audios/videos that have the term "IRS" in them. Then listen to any more that will strengthen your understanding of the common law of the people.