I think it has alot to do with a person's time as well. For someone who is disabled or never leaves home, it may be possible to be available 24/7 but most people are not able to dedicate enough time to be sure a single duck is forever by their side, day and night. Also, it may be the person's choice but a duck prefers to be with another duck. Orphaned monkeys will bond with wire mothers but that is no reason to separate them from other monkeys. I make sure our ducklings are sold in groups of four or more to prevent one from ever being alone.
I am sorry if I sound harsh. I have seen several threads where people end up with lone ducklings and it makes me sad for the poor ducks. I don't think people realize how traumatic it is for the lone duck, especially a baby. Their crying is heartbreaking when they are separated temporarily, I can not imagine putting them through that for life.