We all post for a reason. We do. Many will tell you that no, that they do it because they just "feel like it." That's not necessarily wrong, but that's also not right.
My writing this article has its own reasons. I could just say that I'm writing this because it's "something that needs to be said," but that would only be part of it. Why do I think that? Maybe I made this because I have been thinking it and need to write it down to think of something else. I may just feel alone and unproductive and attempting to fill that emptiness by getting something done. Why am I writing an article in the first place? The reason doesn't have to be complicated, nor does it have to be glorious. But there is a reason I'm writing nonetheless.
Now, a little bit about social media. People's relationship with it gets treated like makeup most of the time. When you ask why someone uses it or posts on it, they dismiss the question and answer that there doesn't need to be a reason. They just "want to," except that's just not correct.
Whether it's to feel validated, to get back at your ex with a couple of pictures, to feel less lonely by posting a picture with friends, to appear as a more attractive person (both for social or sexual means) by showing cool places you've been at around the world, there's a reason why we post.
They don't have to be bad. Maybe you just want to build your online presence to improve your credibility towards possible future employers. Maybe you just want to have a good profile that people can search if they are talking about you to someone else.
Regardless, we tend to forget that, like makeup, it's something that we apply to our (online) appearance in order to paint it how we want to look. Again, that's not necessarily bad, but it's certainly something we can't forget.
And there's nothing wrong with that, as long as you don't lie to yourself while doing it. Know why your post. And even better, don't deny it. It doesn't have to be bad. We post for different reasons.
Just remember: you can fool the world, but you can't fool yourself. At least not forever.