Why do so many Post Office workers make chit chat and go as slow as possible?

Some smaller offices try to relate to the customers more in order to continue to receive their business. If you are having an issue with your local office, call and ask to speak to the Postmaster/Station Manager of that office and voice your concerns. It could be something as simple as coaching needed on the part of the employee in order to get them to recognize that they may be taking a little too much time with each customer.