User file locations

I was just noticing that /root directory is a hard location but /home is symbolic link to /usr/home.
Why doesn't /root sym link to /usr/root?
Obviously it's the administrator account I just wonder why its under / and not /usr/root.
Because /usr may very well be on a separate file system, and the root account needs to function even when all other file systems (other than the root file system) are not mounted.

(Side remark: I've never liked the convention that regular users home directories are in /usr, and that /home is just a symlink. I always fix that on my systems by making /home a really large separate file system. Like that, there are only two file systems that regular users can scribble on: /tmp and /home.