Because changing one thing that has a huge impact (the manufacturer) is a lot easier than changing hundreds of millions of things with each a tiny impact (people's habits).
Or you can decry society for doing the easy thing, but remember that trying to shape outcomes when dealing with large numbers of people almost always leads to consequences that seem obvious in hindsight but were unpredictable at the onset.
I think the "education" aspect has been attempted and it's not working. It's time to go nuclear and have the government dictate what types of materials can be used for packaging and ban everything else.
If I never see another blister pack it will be too soon.