I'm sure many of them got frozen over the years.
Awhile back there was a strange... bug shall we say... where high end items seemingly disappeared from accounts. I and many others had storage accounts loaded with different things and at some point they were just *gone*. I'm not sure if TNT went through and deleted items that were on shell looking accounts, or if somebody managed to get into the storage accounts of a ton of people. I'd lean towards the former.
I do still have a few accounts with duped items from WAY back that I pull from when I need some quick items to flip for pure and things like that - but most of them were frozen or otherwise gone.