Not to defend someone who wants to pollute, but the reason may be to clean up the engine compartment. You have to admit, that cannister is not the most attractive component under our hoods. Before you flame, I still have mine
Good points. Most emmision equipment is designed to make the engine more efficient. In most cases, this means less wasting of fuel, or cleaner exhaust. The cases where emmisions goes up against performance are harder to defend.