This may not be rational, but there's some research showing this is a widespread phenomenon. Mostly, it has to do with a sense of fairness. Coupon codes can make consumers feel like the merchant is being unfair, which leads to dissatisfaction.
The solution: don't show the coupon code field or make it extremely easy for consumers to get coupon codes. I've noticed more and more stores put their coupon codes right in the header while you're browsing. So it's impossible NOT to get a coupon.
actually, no, although that's an interesting place to do it. as a few others have commented, merchants like Newegg and Gap use something like a HelloBar to highlight their coupons in the header nav.
The solution: don't show the coupon code field or make it extremely easy for consumers to get coupon codes. I've noticed more and more stores put their coupon codes right in the header while you're browsing. So it's impossible NOT to get a coupon.
http://www2.owen.vanderbilt.edu/mike.shor/research/promo/jpb... (https://news.ycombinator.com/item?id=6205769)