For anyone who like me, watched the quick look and was left clueless as to the use of those big gold keys - here is your answer. During the story mode, there will come times where you must have a required number of keys before you can continue. It's best to know this ahead of time so that you can make sure to grab them on the way. Having seen the quick look I figured they would relate to a secondary objective and didn't bother, which means I now have to replay a level and pick up an extra key to continue. 

Yup, pretty much. Good job pointing this out to people.