Because no one else will manage your career for you
Career management is one aspect of the modern workplace that is rarely discussed. Answering the question "who's in charge of my career?" should be one of the first lessons you learn in school. Unfortunately, that is not the case. That's why a lot of professionals are shocked when they enter their first job. This is also why a lot of professionals consistently blame others and keep getting frustrated that they are not advancing in their careers.