Why should it be left to the states when there is an argument to be made that because of interstate commerce you need to implement a mandate at the federal leve

Why should it be left to the states when there is an argument to be made that because of interstate commerce you need to implement a mandate at the federal level if you are to avoid a race to the bottom? What is wrong with federal laws for the general good? The EPA and FDA fall under that very idea. Would you rather have food and drugs managed at the state level? We've already seen what happens if environmental concerns are managed at the state level [1]. [1] http://en.wikipedia.org/wiki/Acid_rain#History_of_acid_rain_in_the_United_States http://en.wikipedia.org/wiki/Acid_rain#History_of_acid_rain_...