Isn’t coaching basically “non-professionalized” therapy? Like insofar as a decent chunk of therapy is this^ (interrogating belief systems), there’s hardly a reason you need someone to do it from the blessed perch of a paper that says “Doctor” on it, and hardly a reason your beliefs need to be pathologized to the degree that you become a “Patient.”
Coaching should focus on work issues and your personal development in the workplace. While that does overlap with regular therapy, regular therapy can involve family and more complex personal issues. You may also expect a coach to have more experience in corporate life than a therapist may. But the central tenant is their that the only change that can happen is the change that you make.
HBR has a good podcast that is run by Muriel Wilkins that is useful for those that can learn vicariously.