Why are the words shake well before using not on a milk carton?

The phrase "shake well before using" is typically not found on milk cartons because milk is a homogeneous liquid that does not separate like some other products, such as juices or sauces. Milk's components, including fat and water, remain well mixed during processing and packaging. Additionally, milk is pasteurized and packaged under conditions that prevent separation, making shaking unnecessary. Instead, consumers are generally advised to keep milk refrigerated and consume it before the expiration date for optimal freshness.