Hoarder: “A word that describes anyone that feels the need to find, collect, keep, [or] pack any and everything because they do not know how to throw things away” (Urban Dictionary).
Several years ago there was an entire TV series about hoarders. There are entire companies devoted to helping hoarders clean up. And there are even medical disorders related to hoarding. Innate within each of us—to varying degrees—is a desire to hold on to something.