i dunno what kind of area you're from (whether its densely populated or pretty rural) but if you go to a pretty populated place, maybe a busy highway and you just sit there and look at all the cars, trucks, buses and things that go by, all consuming gasoline and diesel
there are SO many cars out there pumping out so much exhaust gases... and just think, that is just in your area.. you still have the rest of the world to consider..
so i am personally glad there is at least the requirement to have catalytic converters on road vehicles