TÜV is short for "Test und Überwachungs Verein." The infamous German traffic regulatory commission judges vehicles on a bi-yearly basis and decides if they are road-worthy or not. Every motor vehicle must be inspected every two years; modification and tweaking is frowned upon. (Note how this would be a German-inspector frown, the kind that would make even The Grinch's blood freeze.)
While the test costs only $25, it's a royal pain and $25 dollars which could be spent on something else. But maybe there is a good side to it - one sees a lot less run-down / high-pollutant cars in Germany, plus it ensures that every car is fit for the Autobahn.