That's the thing about a democracy, it's hard to screw over small vocal minorities (which the convenience stores and tobacco companies would be if you tried to screw them over). A minority (such as environmentalists who care strongly enough about this to want a law) can't just rule by decree. The environmentalists would need more resources (resources = money and people who care about the issue) on their side than the convenience stores and tobacco companies have on their side in order to get a law like that passed and in practical terms that usually means getting the apathetic majority to not be apathetic the issue at hand. I see that as being very much an uphill battle in this case since the law is against the self-interest of every smoker who would have to bear the cost at point of sale.

Pursuing biodegradable (in a non-geological timescale) filters is probably a better all around option anyway since even with a deposit not all soda cans make it back, compliance for something like cigarette butts would be far less because of the issues outlined in the article.