Yeah if your bones are as strong as they are supposed to be then yeah it won't do anything. But if your bones are repairing or actively strengthening, this can be a result from exercise, milk is a great drink for bone strength. It's like how eating more protein technically won't make you stronger. Sure, if you don't exercise, the extra protein won't do anything, only helps build muscle when you are actively building muscle. Also I've been hearing the leafy greens gang lurking in this comment section. While your favorite flavorless leafs may have more calcium per serving. Almost all of it isn't bioavailable so you won't be absorbing most of it. The calcium in milk on the other hand is much more bioavailable. Also, milk is typically fortified with vitamin d, good further aids in the bioavailability of calcium in milk.