Some people have been mercilessly mocked/teased, bullied, abused, laughed at when they were younger. This can scar a person psychologically and causes them to withdraw in society. It also causes severe anxiety disorders over time, which increases the fear of talking. It takes a lot of psychotherapy and CBT treatment to get over the psychological effects of living with a stutter all your life. It’s not as simple as switching off your anxiety and just saying “Fk it! I’m just going to talk and stutter all I want!”