Passwords, credentials and other high-risk high value intangible data are not associated with high-risk high-value AND our memory is not designed for random junk.
Maybe an anthropologist can study this phenomenon further.
We already have hints of that: our memory has evolved for thousands year to easily memorize places and spatial navigation, in thr past for food, water and danger. Today you go in a foreign place, just one visit and you know where everything is. At the same time, people can usually hold only ~7 concepts/numbers/objects in their head.
In memory competitions people leverage our spatial prowess with a technique called the memory palace, that was already used in ancient Greece and Roman Empire to recall anything, from bard tales to the Iliad and Odysseus.