Back in the day my dad did this as well and I never understood why. We've got a cupboard full of all his CDs/DVDs which he never touches and are pretty much obsolete in this day and age. He's got this filing system to rival a national library but I've never seen him pull out a DVD to watch a movie again haha.
I personally store all my downloaded stuff on a 3TB hard drive which is constantly connected to my laptop to rack up those
seed points. It's getting full though so I'll most likely be investing in another one soon and getting a USB hub to have everything running round the clock.
Come to think of it I think we all suffer from some element of hoarding
lol.