Channel key was never made to be used on every public channel, honestly believe it was made for the HA+ team to use on their channels, without needing to give channel admin out as it allows editing, etc.
Channel Key is basically just allowing access to a channel regardless of password or join power (allowing people to join Joah's channel for example without "Community Legend")
Channel Admin is the default group that should still be assigned by Head Admins.
Channel Ban is not something to be used very often as it's permanent unless manually removed by someone like me. So for example, a CMDR decides to ban someone from his Battalion channel, but once he is replaced, and the person he channel ban isn't black listed, should still be allowed to join said channel. Again, these channel moderation groups weren't made to be extensively used by the public, but more so tools for the HAs and other Admins to use as their desecration.