Since people make mistakes in categorization and sorting, recycling facilities have to do it over again. It's redundant. So why do they never the less have people sort? It's just a psychological tool: It makes people 'care' and it makes people think society at large, including the recycling company cares. Now, that doesn't mean the company doesn't care about recycling in and of itself --they probably do to some extent, but they also need to project outwardly that they care.