What about the cogs and the derailleurs?
And if it rains 3 days in a row?
What I would consider part of the drivetrain.
I ride my commuter bike and pedicab in all conditions.
Nice drivetrains on both.
SRAM dual drive/X9 on my pedicab. Dual hydraulic disc brakes rear, magura hydraulic rim up front.
It is a real piece of equipment that really gets used. Sometimes in significant rain/water/runoff.
Water doesn't bother it that much. It is made out of metal in england.
Just wipe down the drive train and keep it lightly lubed.
Same with my all conditions commuter.