Re: I don't like change
It's been a long time since I had separate /usr… in fact /usr used to be for users' home directories, it's in the name, user.
Binaries wound up there because someone many moons ago ran out of disk space, and so they developed this convention of "user binaries" versus "system binaries", hence the distinction between /bin and /usr/bin. This lead to /u (SCO) and /home (BSD, Minix, Linux) being where users' homes moved to.
Today, separate volume for /home, and perhaps /var in servers, is warranted, but not so much /usr, and it can harmlessly be folded back into /.