On the other hand, if I buy something at Bed, Bath and Beyond or almost any clothing retailer without a 20% off coupon, I do indeed feel like a chump. If the cashier in a store I've never been in before asks 'do you have any coupons?' after ringing me up, I definetly feel like I've screwed up, but I'll still finish my purchase because, well, instant gratification and societal expectations and all that. But I'm not going to go back to that store until I DO have coupon.
So maybe it depends. If your shtick is 'Never pay full price and find ridiculous discounts,' coupon fields might be the way to go, as long as you always have coupons available. But if you expect even some customers to pay full price, having your cashiers ask everyone for coupons is probably not the best practice.
The article doesn't even suggest getting rid of coupons, it suggests putting them in a different spot.
You hit the nail on the head with the first part of your comment -- you decided they weren't worth the time, and therefore you don't save the money. You don't huffily dump your items and leave the line. No, you think, "Hm, maybe I should clip coupons next time." (Although, of course, you don't.)
I guess the risk of using an analogy is they eventually break down if you go too crazy on them. I made it a "real world" example to look at the online experience another way so that people could perhaps relate to the original's author pet peeve. I think if the author of this original article felt like he understood how to get a coupon for the site he was on and decided not to anyway he wouldn't have written the article. Subtle but important point here.
Biggest one is Bed Bath Beyond. If for some reason Amazon can't wait and I need it now, no way in hell am I buying a product from that store w/o the 20% off coupon
But you don't need to imagine it because it happens all the time and you still shop in stores.