As somebody who makes a lot of their living looking at how people express their thoughts on the internet, it is beyond me why some of us enjoy doing it with such candidness and regularity. It might make for good entertainment, but it's not exactly the best way to process things.
There are many reasons why so many people are prone towards this, but a big one that has influenced the current landscape is Facebook. It acted as a mainstream introduction to sharing oneself on social media, encouraging everyone from the overly online to groups who had barely so much as looked at a website before. We might be a world away from what it was at its influential peak, but it still produces some of the most reliably deranged content from time to time. There will never be anything quite like it again, so we should appreciate it while it lasts.