He just kind of drags a folder or file to the window, which may have a list of many folders and stares blankly, like a cat, then drops the file somewhere there. He has been instructed to drop it on the background surface if he want it in that folder and on a folder if he wants it in there. Doesn't matter he forgets and just does.

When I force him to use right, click-copy/move or ctrl+c/v, he is forced to think about what and to where.

I think he doesn't want to think. Mental bump to overcome that he avoids. Exactly what old people should not do. He needs to be forced to use that brain.