However, there is room for more support in your journey.
I always tell my clients that their partner is the person with all the knowledge about them and I am the one with the benefit of expansive knowledge on labor and birth and our goal should be to work together to support the mama through her birth. It is my passion to continue to learn about birth, to take more classes on labor and comfort measures, to process and grow from each experience.
In the intense moments surrounding birth it is a calming force to know that you can focus solely on your partner and allow your doula to whisper the next idea into your ear, to guide your hands to a comforting position and to remind you of that next position to help the mama into.
Your doula is fully invested in your birth but has a greater ability to separate herself from your specific experience and draw from other births to help you cope in your labor. Occasionally partners have a rough time seeing a loved one in pain and it can be helpful to have an outside view point to remind you of your mutual goals and previously discussed wishes for the birth experience, while supporting any changing desires throughout the birth process.
Also, sometimes the partner is indeed so in tune with the mama and so involved in each moment that they themselves forget their own basic care (eating, resting, breathing) and your doula is there for them as well.
In the end my job is to support YOUR ideal birth with as little or as much involvement from the partner as YOU desire.