Both of my parents grew up during what is now called the "Great Depression". They did not throw things away because they felt they might need them sometime. Our house was not a mess. In fact, my mother was a good housekeeper. They just kept things longer than I might.
I have seen a few episodes of the television show about hoarding. Some of them let stuff get piled nearly to the ceiling. It creeps me out to think what may be living underneath all that.