How does one know if their discount code is getting used? We don't! How can we run different promotions and know which one is most effective if we can't track the number of uses a discount code gets?
OR is not very friendly to marketing efforts, and this needs to change. Marketing is becoming much more important as competition increases.
You can already run a line item pivot or line item detail report to see where the charge was used.
Admittedly, this isn't ideal - we have a design to create a separate report for this purpose.