You said it yourself… you don’t know one man who would 

take time out of his day

The things you mention are vital. They are the essential parts of the relationship. But one of the several reasons poetry is something some people appreciate is that it indicates someone took time out of their day to focus on you. 

To think about how you make them feel, and want to share that with you in a beautiful way. 
They wanted to make something beautiful in your honor. 

It’s a diamond necklace indeed. 
You can’t build a relationship out of diamond necklaces; not all poets make good spouses. But a good spouse who does things like that as well is not something to be trivialized, but treasured and emulated.