I’m curious why the separation between these still exists, because a bunch of distributions symlink all of these to /usr/bin either way
It exists because, long ago in a galaxy far far away, a sysadmin ran out of space on a drive. The system was split between two 10MB(?) drives, one was / and one was mounted at /usr, for User data. They moved some of the programs to a folder for a dummy user, /usr/bin, and put that in everybody’s PATH.
Everybody kept on doing things that way ever since. Social momentum is funny that way.
Think about booting over network. Or having /usr on another drive. Including even network drive. Think about dumb terminals(wrong cetury) thin clients. For example they can use small disk to quickly boot wihout downloading kernel and initramfs and use NFS for /usr and /home.
These days, AFAIK network boot is done thru initramfs. It loads rootfs in most cases I’ve seen tho.
