But, I in a way int kind of makes sense.
/bin and /sbin, needed for system boot. /usr/bin and /usr/sbin for normal runtime.
's' for items regular users do not need to run, remember, UN*X is a multi-user system, not a one person system like macs, windows and in most cases Linux.
Nowadays most Linux systems boot with initramfs, that is a compressed image that includes everything the system needs to boot, so you're basically saying /bin and /sbin is useless.
Not always (raise your hand if you've had an unbootable system due to a broken or insufficient initrd).
In retrospect, the whole concept of the initrd seems like an enormous kludge that was thrown together temporarily and became the permanent solution.