The distinction between / and /usr has historical reasons. Back when Unix systems were booted from two tapes, a small root tape and a big user tape. Today, we like to use different partitions for these two spaces. The Hurd throws this historical garbage away. We think that we have found a more flexible solution called union filesystems, which allow to create virtual filesystems which are the union of several other filesystems. However, support for union filesystems is still in early development.