We look in the mirror and see so much of ourselves. Before facing the big world, you judge yourself in your own court room, determing whether you have the looks to go out there and kick ass and take names. People may think that they are not ready to show themselves simply because they have low self esteem or maybe they think too highly of themselves. It all comes down to one thing between both of these types of people: insecurity.
Taking a selfie addresses both of these types of people. A person with low self esteem may be too shy to post their selfie because they are afraid of not being popular enough and they may not get enough likes or comments. The people who hold themselves in high esteem may post many selfies to get at much attention as they can. Being comfortable with yourself is an important factor to post what you want people to see.
If people don't get to see you, they won't get to really know you. On the other hand, expressing yourself too much with your selfies can push people away because they are bored of seeing your face. However, it also depends on the significance of your selfie picture where you may get attention. An example would be you taking a selfie at the top of a mountain after a long hike. Another example would be you taking a selfie after you dyed your hair or you take a picture with a friend you haven't seen in a while.
Being a wall flower doesnt get you any where if you want to be noticed on your social media, and "whipping it out there" may make people just fly by your post, not giving it a second thought.
Be comfortable with yourself and don't give a care about what other people will think of what you post. It is what is it, so sit back, relax, and snap away. Own it baby, you were born this way.