They missed one reason why it can happen: Because doing things "the right way" is too slow, and the engineer is trying to skirt around process because the company moves way too slowly. Not out of malice or negligence, but out of a fear of the megacorp killing agility. I've seen entire teams at megacorps or governments try to keep others in the dark with projects that would be crushed under strict corporate rules.
It doesn't have to be a megacorp. Looping new people into a deep problem takes time, and can kill momentum if not done in a strategic way. Your personal time on any problem is finite, and you can exhaust that time-budget on bringing the wrong people up to speed. This is doubly true when the other person isn't on your team or in your organization: e.g., bringing in vendor support. (Maybe your experience is different; in mine, bringing in remote experts doesn't guarantee a faster resolution.)
