Well this card says "Share your experience online and save 15% on your next visit...."
Are they trying to make the connection that you get the discount when you leave a review? Quite possibly. However, why then go ahead and provide the discount code without first requiring the review? The code is "DIRECT" which to me suggests they are trying to get you to book with them directly, so they save on booking engine fees.
I agree that a discount is not even needed--and if you read my post, that is not the focus of my recommendation. I certainly wouldn't recommend offering a discount, as it is simply not needed.
Just asking for a review is what a lot of businesses fail to do. :-)