It's not always intentional though. I've become that person simply because I wasn't allowed time to even reflect on what I'd done, much less write it down. Sometimes it's the person who is just naturally good at problem solving and if you ask them how they did it, you get a blank state at first at if you'd ask them how they make their heart keep pumping. Most issues like this are systemic issues, not personal failings.
That said, I've known some pretty toxic people who hoard knowledge like it will protect them. That is not good. But also comes from a place of fear which is, again, a systemic issue
