Have you ever heard of hoarding? My mother is a hoarder. She has 500 pairs of shoes!
Yes I have, sometimes people have an attachment to something they don't need. She may think she'll need each pair for something.
I guess so. I think maybe it is some kind of anxiety disorder.
Anxiety can be caused by environmental factors. Maybe the hoarding causes anxiety and it creates a vicious circle.
Maybe so. I wonder if some kind of medication or therapy might help.
It is worth looking into, it can be a health risk to compusively hoard.
Yes, first it is shoes, next it could be something else. Have you ever seen the show Hoarders on tv? It's scary. 
Yes, it is really bad if they don't have the spaces to cook, clean, or sleep. It can become debilitating.
Yes, and then it seems like the family members cannot talk any sense into them. They have to have interventions. Sometimes the local authorities will condemn the home as unsafe. 
It could block an exit during a fire, collapse on someone, or even become rotted or infested with bugs and rodents.