This thread is swinging toward a Microsoft mind set and Linux just doesn't work that way, it was built from the ground up with security and networking in mind (developed by lovers of the OS on the internet, so it had to be designed that way as it was designed as a minix workalike).
I just let /bin and /sbin stay on / as they are so tiny.
Linux and the Tools Philosophy
du -sh /bin
du -sh /sbin
A worst case re-installation or distro change is too quick and easy, so I can't see any point in making separate partitions just for the binaries. Every partition requires some overhead space as well, so the disk ends up with more usable space with fewer partitions.