Sharing ideas can be done in written form but it is oratory i.e. public speaking that appeals and persuades the masses. The same thing applies to politicians at any level of government. When they are running for office they may send us some written material but it is there public speaking that gets them elected … or perhaps not!
In my early adult years, I was a professional Registered Nurse. I got involved with my local professional organization. It was easy to get elected, likely anybody else was too fearful to run for office. What was limiting to me was my fear of public speaking. While I had the desire to be a leader, my leadership skills were rudimentary at that time. My lack of public speaking skills limited my advancement in the organization and in time put limitations on how I was able to perform the role that I did have.
In summary, you can lead a professional life without ever having to speak in public. Countless numbers do. However, being able to speak in public as a professional has a high likelihood of increasing opportunities, the ability to create change and a deep sense of personal satisfaction.
Thanks for your question.