It's a convenient way for many people to shift blame for their own shortcomings, and its way easier than working toward better health.
These things become psychological contagions, and these contagions can spread quickly online.
People are tribal, so they can form tribes around these issues. They even get special treatment in society too, and who doesn't want to feel special? 

It's got to the stage where mental health issues are used as badges of honour, the more the better.
Just look at corporate social media profile bios.