Because it works, well. I use green 20/20 premix + a tube of the MB stuff or 303 Instant Windshield Washer Tablets with great results. Definitely better than using nothing. I live in Seattle and battle constant misty conditions and short days in the winter, so clean windshields are important to me. Wurth also makes a very good concentrate, but still is better with the MB stuff in there.
1986 300E Anthracite + ECodes + MB Mileage Award