I've done work for the kinds of retailers who have coupon code boxes, and most of the time, the only reason it's on there is because the default WordPress plugi

I've done work for the kinds of retailers who have coupon code boxes, and most of the time, the only reason it's on there is because the default WordPress plugin/Joomla template/eCommerce solution has it there. No one ever thinks to remove it, despite them never planning on using it. The best way for coupon code boxes to stop appearing is for developers and designers to bring it up with their client. A lot of the time, once the client is actually confronted with it has to make a decision, they choose not to have it.