Advertisers think it's okay to leave unwanted stuff on other people's property and force them sort out the mess. Roommates who did that would be told to knock it off by the people they live with. Why should people accept the same behavior from advertisers who are total strangers?

They are counting on people being decent human beings who do what they're supposed to do without complaint. That's exactly what enables them and lets them get away with their unacceptable behavior. If nobody did that, maybe the situation would become unmanageable and the city would be forced to deal with it.

The right thing to do is to put an end to all advertising. That's the true solution. Nobody's gonna do it because the money speaks much louder than right and wrong.