It's like work email. Mine were 100% read for 16 years. Then I let one go unread, then two, and now I'm up to just under 1,000 unread emails. It's an adrenaline rush, like Russian roulette. I doubt I'll read any replies to this comment! I need help.
I have tons of those. I still mark every single one of them read. Only time I ever leave anything unread is when I need a reminder to get back to it later.