A common theme with hoarders is that they'll acknowledge they have too much stuff in general, but when it becomes time to get rid of an individual item, they always have a reason to hold on to it. For my mother, the reason she hoards is 100% due to things being "heirlooms" and every individual item having a story. After her dad died she couldn't throw away any of his old stuff because she grew up with most of it and it reminded her of her parents (who were at that point both deceased). It's a difficult situation because it's quite reasonable to hang on to a large number of old items, just not all of them. But each individual item still seems incredibly important to her

In the case of my grandmother, she'll definitely make up a story behind an item she doesn't recognize (and you happen to.) It's just a simple fear of throwing or giving things away - but so disguised that I couldn't tell until I noticed her clinging onto some of my old things that I had thrown away, and her not knowing that they were originally mine.