It makes the whole thing the problem of whoever survives. By not leaving documentation, you pass the work of picking up the pieces to someone else. I think "selfish" might be a little strong, but it's not an indefensible position to take.
This depends on what we're defining as documentation vs access. My interpretation of the start of the GP was more about passing over actual login/access information, which especially for assets and finances really shouldn't be handed over this way.
Documentation in the form of "I have a bank account at Bank X, and a will at Lawyer Y (or, I don't have a will, but there are established protocols to handle this)" (even if only verbally) is different than "here's my username and password to my trading account in case I snuff it".