Therapy is very important and needed to help people heal from mental health disorders, i.e., trauma, PTSD, depression, etc. This work is highly treatment-focused. Coaches do not work with people with mental health disorders.
Another important difference between coaching and therapy is that unlike therapy which focuses more heavily on the past, coaching focuses on present and future but will visit the past to gain context within the current situation.
Because of this distinction, a person working with a licensed therapist to heal from mental health disorders can also work with a life coach to receive additional support with current and future life goals.