The difference is in the employment structure:

    * The majority of doctors are self-employed
    * Farmers are, by definition, owners of the business
    * Executives tend to be large stakeholders in the companies they manage

Institutional school teachers tend to be employees, although I'm not sure about all teachers. However, I did have at least one high school teacher (from years ago) tell us that in the future people would learn on demand over the internet, which is coming true, and largely being provided by people who do not have teaching backgrounds.

I expect programmers also tend towards being employees, and thus there is a strong interest to automate/eliminate that work.