Why do people post so many pics of themselves?

Ever since social media came out, I have never really posted a pic of myself. I'm an young adult and I am definitively in the minority. It's just that I find it unecessary and I don't think I look good in photos. I also don't really understand why it has become so popular, I mean it's not... show more Ever since social media came out, I have never really posted a pic of myself. I'm an young adult and I am definitively in the minority. It's just that I find it unecessary and I don't think I look good in photos. I also don't really understand why it has become so popular, I mean it's not necessary in order to communicate with people. In my own experience people are using it more and more and I am starting to feel like an outcast sometimes. I remember it used to be attention seeking to post many pics but nowadays even young teenagers post lots of pics of themselves. People, like psychologists, who also talk about how it affects us negatively, also post lots of pics. I don't have anything against them, but I just don't understand the need for it. There has to be some good reason so why is it like this?
Update: @Dv8s this is what I have thought but it's just so common that I can't believe everyone has self esteem issues.
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