Question about the tv show "hoarders"?

I went to a trade school years ago where they had a teacher who was a "hoarder." She had trash everywhere in the school. When she took a two week vacation, I threw all that junk out. When she came back (she even saved milk bottles), and saw everything gone, she went to a dump and brought back everything she could replace; in one day. What is up with that? Even her car was completely full of trash.