What is the point of using a links object for relationships in Ember Data

I am trying to understand what the point of the links object in a given payload for specifying related resource endpoint locations. Isn't this the point of an adapter, to specify where that resource data endpoint is located?

I would expect Ember Data to lookup the models relationships, and then invoke the correct adapter to get that resources location. So why then do I also need to include the links hash to describe this?