I upvoted you because of your first paragraph. But OP's suggestion isn't absurd. One might still offer coupons while not making the option obvious to people who

I upvoted you because of your first paragraph. But OP's suggestion isn't absurd. One might still offer coupons while not making the option obvious to people who don't have one. > How is it bad customer service when a user literally isn't forced to do anything other than ignore the field if they so choose? This isn't simply OP's opinion. Some people will get pissed off if they found somebody else just got a better deal. E.g. see recent Paul Graham's essay where he mentions some investors will refuse to invest at valuation $x if they find out another investor got to invest at valuation $0.8x, (with the implicit assumption that they still believe they can make money at the new valuation).