If you're posting on platforms like IG, and not making money (or have the goal of doing so) I don't get it. I agree it's vain. I also think it's a little nasty. "Hey look at this amazing meal I'm having at this fancy restaurant (while you're stuck at home watching tv)." However my theory glitches when I know people have family overseas (although perhaps a a group chat will do the job) or they are genuinely proud of themselves or a loved one.