Why do some rubber ducks not squeak?

Not all rubber ducks squeak. This is because squeaking is a feature that is added to rubber ducks during the manufacturing process. The squeaking mechanism usually consists of a small air bladder or valve inside the duck that produces the sound when it is squeezed. The reason why not all rubber ducks squeak is most likely due to cost and design considerations. For some rubber ducks, the cost of adding a squeaking mechanism may be deemed to not be worth the additional value it provides to consumers. Additionally, manufacturers may decide not to add a squeaking mechanism to certain designs to maintain a particular aesthetic or to focus on other features such as durability or texture.