Why can I only pay social security in Nanjing?

There is something wrong with this system. In this case, I bring my valid certificate and social security card number to the window of the service hall of the local social security bureau for enquiry. I can only pay social security in Nanjing, but there is something wrong with the system. My Nanjing is a municipal public service mobile application software that integrates all kinds of life information of Nanjing citizens. It is based on the construction of a "smart city", with the aim of "information benefiting the people", and the goal of the majority of residents staying at home and enjoying quality services and convenience anytime and anywhere.