By reading this "job description" for project managers I still wonder why on earth would people think management is a natural step in a developer's career path

By reading this "job description" for project managers I still wonder why on earth would people think management is a natural step in a developer's career path (at least here in Europe). These are different jobs entirely! How are the experience, knowledge and skills I earned from studying and writing code for years going to make me any good in dealing with people in the future?