Without rules, metadata, systems to organize files even the most valuable data can be stored as a steaming pile of poo. In my case I was diving into a compressed tar containing compressed tar-s, which again may have giant uncompressed data files inside. The whole pile of crap had premature EOF so for sure some non trivial amount of data was lost. And on the top of it what was preserved should have a prefix: "unobtanium_". Storing several tar.gz several terabytes in size on some puny domestic use NAS made extraction of the files a crying game.

In another site I found a mix of some old version windows disk images with data. With more crap inside.

In the end: storage may be cheap. Storing piles of disorganized crap is very costly if you want to find something