For example, on Discord, I sometimes see people with unreads for every server, and dozens to hundreds of completely unread DMs, just because they don't know that you can turn notifications off for the stuff you don't care about. Instead of doing that they just learned to ignore everything, leading to a disorganized mess.
I'm somewhat familiar with what typically leads to this (usually something like ADHD), but when you let it go for so many years it's such a big task to fix it that the fixing never happens and you're just kind of screwed for eternity.
In Discord, I have no unread servers and no unread DMs, despite being at the server limit. This is because all my servers are completely silenced and all my DMs are read immediately. My only unread email is one I marked as such because I still plan to reply to it soon. I have the attention for every single notification because I aggressively optimize the notifications I receive to the point where they all are typically things I care about. Back in the day I would instantly report every email to SpamCop, typically in under one minute, but I eventually stopped doing that because there's no point.
I simultaneously do and don't understand people who just submit to a flood of irrelevant garbage. Control it!!