As a coach, and utilizing your own experience and expertise may enhance your coaching work in the area or areas you with which you are most comfortable. Your comfort level will be apparent to your client and create confidence for your client to open up more.
If you tap your own expertise, and search out clients that fit your knowledge area, or area that you are comfortable with, then you as the coach have a better understanding of what your client may wish to discuss with you and what type of questions to ask to better serve your client.
Offering coaching services primarily within a niche can maximize awareness of your expertise and motivate you to increase it. It helps clients find you and be comfortable in letting you coach them knowing that you have the understanding of what they are talking about.
Alternatively, sometimes a lack of expertise is a benefit. If your expertise is limited, when you ask the client questions and they explain, the awareness for the client is enhanced because they are called to be very clear in defining situations. Additionally, they consider the perspective of people they want to reach, their prospective clients or customers.
Often a balance of some knowledge with a focus on process expertise is the best of both worlds. Too much knowledge may lend itself to preconceived ideas of how something is best handled whereas some knowledge lends itself to a full exploration and at the same time empowering the client to decide their strategy.