It's a problem if someone consumes no dairy products, or very little, and doesn't also eat anything else that contains calcium like spinach for example - but once your body has had enough for its normal processes, having any more isn't helping you. Drinking a litre of milk every day won't give you stronger bones than someone who drinks one cup. And all that milk you are drinking is just increasing the amount of energy you are consuming, meaning you are putting on weight or else have to exercise more to maintain your weight. Not to mention, milk costs money, whereas a glass of water from the tap probably costs a fraction of a cent. And one last thing, that glass of water likely contains flouride, which is protecting your teeth, whereas milk is contributing to their decay.