I think these are excellent laws which prohibit people from purchasing just one or two chicks or ducklings. Given the very low price of purchasing just one or two chicks and how cute they are when they are small, there is a very real temptation for people who have no knowledge of how to care for them or their social needs to purchase them usually condeming the chicks to a very sad and very short life. These laws exist for humanitarian reasons.
My guess is these laws have very small penalities that are rarely enforced against the stores. The existence of the laws with minimum penalties gives the stores the ability to defend its refusal to sell just one or two chicks to people who are buying them on the "cute and cheap" factor yet still look the other way and sell a couple chicks to a responsible hobbyist or a customer willing to make the investment in a heating lamp, feeder, waterer, wood shavings, feed, etc.