Successful businesses need a variety of people to achieve their positive results. Similarly, the most successful people know that they must work together as a team with their co-workers. It is important for you and your success to have people working with you that provide strengths in the areas where you are weakest. For example, you might be the greatest leader in the world, but do not like to get into the details. In this instance, you need to be working with people that can take your ideas and enthusiasm and translate them into projects and tasks.
Someone has to manage the projects and tasks to successful completion.
Or, you might be extremely analytical - exceptional at predicting market trends, but lack the salesmanship to convince management to follow your ideas. You need to be working as a team with someone that can provide that salesmanship. You have particular strengths to contribute to any organization. You also have weaknesses. Someone on your team must be strong where you are weak.