The other side of the argument is that people simply won't do it. If you make it difficult to dispose of used motor oil, people will just put it in their regular trash bags and it will wind up in a land fill where it's dangerous.
The towns around where I grew up used to make you pay money to get rid of metal (!!!!). Consequently it wasn't uncommon to find washing machines and old rims in random places. Then a scrap place opened up, appliances stopped showing up on the side of the road and the scrap place that only took copper quickly got ran out of business.
People don't want to dump stuff illegally, it's just the least worst option in the moment.
