Well, basically I agree because not everybody on your friends list are interested in your photo and might only cause a stain in your relationship with them. Researchers said that it’s one way of saying how good their situation is compared to others. Or how attractive they think they are.
But some people noted reasons on why they post selfie on social media. Like for example, they’d like to show to their families who are far from them about what they’re currently up to. Yes, that can be done in private message but it would be trendy if you put in on your timeline where your friends can see it.
PS. I’ve read about the research on breaking news english. Just in case you’d ask. ;)
Steepshot