Filesystems store what we use on our computers. They are not an act of god, they are man made. They seem to have an impressive resilience if it comes to innovation though. The folder / directory structure was more or less the last break through. Since the the storage capacity did grow: You mom might manage hundred times the storage now than a mid sized team of lab coat wearing engineers did when she was young.
This general rant got inspired by an rather unpleasant observation: Many filesystem become unstable or only slow in the better cases when they become full. Xsan and xfs
have technically not that much in common, but you better keep 10% space available.
Which is tragically exactly the opposite from any real life use I have seen. Now I am talking about professional storage for media. It always is full. Brimful.