Having only usable binaries in the path aids discoverability of the system.
This means that in practice people will just add sbin to PATH to get a somewhat usable system, which makes the division between bin and sbin useless.
Furthermore, on BSD derived systems binaries that should not be invoked by users directly (e.g., daemons) need to be stored in libexec.
https://refspecs.linuxfoundation.org/FHS_3.0/fhs/index.html
You may be thinking of the /bin and /usr/bin difference, though.
My memory is hazy but I recall the distinction being / vs /usr not /bin vs /sbin.