A razão pela qual as coisas foram mescladas para / usr e não para / são anotadas em The Case for the / usr Mesclar :
Myth #11: Instead of merging / into /usr it would make a lot more sense to merge /usr into /.
Fact: This would make the separation between vendor-supplied OS resources and machine-specific even worse, thus making OS snapshots and network/container sharing of it much harder and non-atomic, and clutter the root file system with a multitude of new directories.