They're starting to mandate catalytic converter's on LAWN MOWERS... They'll be on all mopeds before you know it.
New York times article on catalytic converters and lawnmowers. (read it before they take it down from the website.) Manufacturers think that a catalytic converter will add $25 to the price of a $180 lawnmower.
People will still buy the lawnmowers if they and everybody else has to shell out the extra $25 for a catalytic converter equipped mower. Even though they have the alternative of using a human powered mower.