As with you, I've also not had a chance to use the coupons, that is until recently. I realized that they're also good for a 10K miles discount on an award, and domestic flights are 10K, so I used one for a free domestic flight without needing any miles, and another I ended up using to discount the miles needed for an international F award ticket. I rarely buy upgradeable class tickets, so the mileage discount is the only way I can use them. But being I'm already Lifetime D+, I guess I'll continue to receive them, though not really a big deal to me.

As for closing down branches, that doesn't surprise me given how connected Koreans are to the internet, and how much they use it for online shopping, etc. I'm guessing more and more Koreans just buy their tickets online, either directly with OZ or an online travel service. In fact there's often discounts available online that aren't available if you purchase the ticket in person. And even for those not buying online, provided you're paying by credit card it can be done easily over the phone. I've been to the ticket office at the CAT in COEX a few times and even that office isn't busy at all. Same with a few other airline offices in Seoul - TG and CX, nobody else in those offices. I think it's just a sign of the times that physical offices that interact with customers are becoming fewer and fewer.