There's a big difference between embedding a url and simply posting a link. Embedding a url, uses a third party service to process the url and return a code snippet to the end users web browser that presents an attention getting preview of the url resource.  
 

Sometimes, people just want to link to a resource without the highly processed preview... especially when such a preview within the context of a post would create clutter, and distract from the main content.  With the link function, you can associate the resource with a single word, such as click here.  I'd have used a real example, but my sorryass membership level here, says I'm not allowed to post links.

You need both the link and url embed, however in your screen shot, a link on the editor menu bar as well as the action menu below, is redundant.