When I get up in the morning, I am seldom very awake. It is not unusual for me to stand in the shower for 15 minutes, get out, then realize I never picked up the soap or the shampoo bottle. Or, as is more often the case, after 15 minutes, come out of my fog, then wonder what I've done. At those times, I pick up my shampoo bottle, try to observe whether it is wet, hence indicating I may have already washed my hair, and generally just "repeat", just to be sure.
This got me thinking. Remember when the shampoo bottle said, "lather, rinse and repeat?" I'm quite sure that's what it said because I always wondered why you needed to shampoo twice. Clearly this was a way to get consumers (me) to use up more shampoo. Did anyone actually follow those directions? Now the bottle reads, "repeat, if desired". Perhaps that means the shampoo marketers still want to use up the bottle but don't want to suggest there's really any need to shampoo again. Someone somewhere must have complained.
If they want to capture true consumer behavior, they should change the label to read "repeat, just in case."