Sider: I never put my shopping cart back, pick up my popcorn box at a movie theatre or clear my table at a fast food restaurant... Not because I'm lazy but because someone gets paid to do that. I'd prefer someone get a paycheck rather than provide a subsidy to the corporate chain of theaters, grocery store chain or fast food franchise.
DFO: As a person who worked his way partly through college as a checker/boxboy for a grocery store, I'll assure you that the simple courtesy of putting the shopping cart back is appreciated. I was slammed with my regular duties, which included carrying out groceries in those days. I didn't have a lot of time to collect shopping carts. But I appreciated those who brought them back to the store door. As far as leaving popcorn boxes on the floor of the theater, I thought that's what the management expects. Then, I've never been an usher.