Generation and serialization of the link section of the response drastically outweighs the the actual data in the response.  Most clients, especially the site, will either hardcode URLs for simplicity or for performance (site won't be doing indirections when urls change, nor can it afford to discover the full heirarchy on each request).  The client should be allowed to indicate to the server that the link information is unnecessary and thus save the serialization and transfer costs.