@kev In this senario, the most possible attack is from people around you -- family, friends etc. They could gain access with relative ease.
Assuming absolute trust on these people, it would be fine. However, it is not always the case in the real world. A kid might want to hide his / her pwds from the parents, or even Grandma might want to hide her pwds from Grandpa.
I believe that, however, this can be used as 2FA: pwd managaer + pwd book, each storing part of the pwd.