3 years in a depression

If you watch the program hoarders , They say right at the beginning How many millions of people Suffer from this problem... Watch that program for a few episodes. You'll see it piled up to the ceiling to where they're crawling on five feet of stuff to get to from room to room..
I can't watch that show anymore, it just makes me wonder why someone would want to live like that. I realize that it is a mental disorder, and I don't personally understand it, but it still makes me wonder. Having said that, I have an uncle who is probably in that state, he has not allowed anyone in the family to enter his house in over 30 years. Barely even has any contact.