Anyone who thinks the license is a scam or not needed has clearly never tried to hire a car in Korea. My husband and I had booked the car and given our license details but husband lost his interntional drivers license. He had a valid HK license, a valid UK license, a valid Australian AND a valid NZ license with him (we've lived in many countries). NONE of these was acceptable and in the end I had to drive.
Similar story in Japan last week.
But you want to know something really fun? We hired a car in Cairns using our (written in Engish) HK licenses last year, and Europcar INSISTED on having an International License! I didn't have mine, and my Aussie license had expired, but luckily my NZ license had about 2 weeks left on it. That worked.
Yes they are a pain to renew, but they can save an awful lot of hassle at the car hire counter.