It would be interesting why this is the case. I suspect it is mainly because there is no one around who would be in a position to allow redistribution of image

It would be interesting why this is the case. I suspect it is mainly because there is no one around who would be in a position to allow redistribution of images. Which would be the saddest possible reason, in a way - if some company or person sat on the copyright and flat out refused to allow redistribution, there would at least be hope for that person or organization to change their mind. But if there is no one left who could consent, that day will never come. Of course, if there was no one left who could give permission, that would mean there was no one left who could complain or sue; but ethical issues aside, I would not like taking that risk.