/usr/bin only existed because of fast small mainframe hard drives and slower larger hard drives.
I don't understand why the direction is the way it is thou. getting rid of /usr/ seems like it would make more sense.
And init binary in /usr is complete braindeadness...
Also MS behind anything means they are trying to get rid of your options, eg by complicating things into "enterprise level" and keep pushing windows as userware.
But there is other possibility: minimal root that is easy to manage, switch, etc. etc. and rest of the system :)
Yeah, libostree ("git for operating systems binaries") benefits from merging /usr. It might even be a requirement to have merged /usr to be able to use it.
Wasn't that basically a historical accident? IIRC in very early UNIX, "/usr" used to be like the modern "/home", but they happened to have a big disk for that mount and started putting system files there.