Civics?

A thought occurred to me while I was flying back yesterday (I had to change my flight due to the snow): Why do we teach Civics classes?

Obviously, I know why in the literal sense - to make sure that the next generation of American citizenry knows how their government operates (or rather, how their government is supposed to operate). But what is the practical application? Sure, the students who successfully complete a civics class (are expected to) know how a bill becomes a law, how the electoral college works, and the system of checks and balances - but what use is it if the government isn't even following its own rules?

Somehow it's fine to trample on habeas corpus, but don't you dare stop the constant stream of penis enlargement pills to my inbox.