Certainly, drivers still toss cups, fast food wrappers and cigarette butts from their cars. Maybe we need a new campaign. Littering creates significant environmental problems. When you litter, invariably what you throw onto the street ends up in a stream, lake, river or, eventually the ocean.
Roadways have storm drains which are meant to capture storm runoff.
Those drains empty into streams or other water bodies. So when you toss that bubble gum wrapper, you may very well be polluting public waters. Even if the water is unimpacted, littering is still a disgusting, lazy habit. We have all traveled on interstates and have observed how some portions of the highway appear to be more litter-polluted than others. That's a great idea even if some find it to be offensive in some manner.