Not to mention, a major part of digestion begins in the mouth. Saliva breaks food down and prepares it to be broken down in the stomach, so that it can be assimilated in the intestines.

When you consume liquid calories, you miss out on this important part of the digestive process (and subsequently lose out on absorbing a portion of the nutrients), unless you are "simulate chewing" or leave the liquids in your mouth long enough for the salivary enzymes to "get to work."

Granted, this doesn't mean you can't survive off of liquid calories, but digestive issues are bound to happen. Nutrient-dense, whole foods should always be the first option.