There are so many reasons people do not get to know who they are. Some people are taught thinking about themselves, and what they want is being selfish. Unfortunately, for those who have no idea who they are, they are the ones who are easily led. They'll buy just because someone else does, they'll even sell for the same reasons. They spend loads of time thinking about what others think of them, doing all they can to please everyone, not realizing it will never happen.
It is important to know who you are because when you don't life gets increasingly hard to live. You begin to develop resentments because you feel you have no say in your life. To a great degree you don't when you measure your reality through the eyes of others. Knowing who you are is not a cure all, but a true beginning to understanding why you do some of the things you do and don't do.
Self-knowledge is also a gateway to understanding others. We are not really that much different and in the ways that we are, they don't really matter. Male/Female, skin color, eyes, nose, ears, etc. We all have these characteristics, but they minimally impact our lives. How we think, what we do, these are the things that make the difference.
Take time to get to know who you are. Learn to like you, you'll love you.