"You get pages of results: mostly garbage, some scams, and a few legitimate coupon sites. Unfortunately, the codes listed on those sites are a year old: you missed your chance."

It frustrates me when I see a coupon code box and cannot find any working codes. Oftentimes the most recent codes for a retailer on RetaiMeNot haven't been active in months or years. On the flip side, when I find a code that saves me anything, even free shipping, I am ecstatic. I feel like I am responsible, thrifty and savvy and I have a proclivity to purchase more items from that retailer later on.

I think these emotions are worth evoking in customers and banning the coupon code box destroys this ability. A referral link doesn't capture as much of the emotional satisfaction as seeing your cart totals drop after typing in a string of characters and clicking "Apply to Cart." Retailers could just hide the coupon code box when there aren't any active coupons. When a coupon is active, the box reappears.