Because it's all about money for the dealers. They cover their asses from warranty issues by using your mods as an excuse for the causes. I heard Ford is not covering any aftermarket parts that they donot sell. I guess Honda is doing the same. I heard on the News that Ford stated that certain types of mods may not be the correct application for the car and many owners damage their cars for that reason. For example, getting wheels that have the incorrect offset for your car would throw off the balance, they believe that it would damage your car. That would void their warranty.