We don't actually, because it's obvious; people should put trash in the relevant bins, and the local authorities should pay people to clean it up. Online discourse is not action. Look at e.g. Japan that doesn't have a littering problem, because people don't litter and they pay people to clean up the rest.

But as others pointed out, this was before plastics, before the availability of the wide variety of products and services we have today, before chain fast food restaurants. They would have had (waxed) paper and the like, but not to the point where it was so cheap that it would be everywhere.