Ok, is the left unit for lighter tasks and the right one for industrial strength projects?  ( ans. No ). 

Is the left unit to wash your dishes when you have a midnight snack eating in bed?   (No).

Is the left unit a unisex urinal for the evolvivg human species?  (No).
The bidette is like the drive up window for washing the family jewels (forward & aft). With this task taken care of without a shower, many European body maintenance managers decide that a daily shower is not needed.

Why do we not use them in the USA?  (How in the heck would I know? ).