GQ answer

Why would I want to put information on my webpage that is not typical on the viewer?

Metadata is not visible to people who view the webpage but it is an initial component to completing a webpage. It helps with communicating important information such as keywords, the description, the author, etc... By typing in these metadata tags, we can efficiently categorize a webpage based on its keywords, description, etc...In addition, it also makes it simper for us to reach the webpage without haveing to do a large drawn out search.