The blockchain will start in Korea at first as it is Spoqa's base of operations and the founders of both Spoqa and Carry Protocol wish to start small at first with their most loyal merchants. This is to prevent Carry Protocol from overextending themselves too fast, I assume.
As for the why this needs to be a blockchain, in my personal opinion it has to do with the anonymity and cyber security that only the blockchain technology can provide to ensure the data protection of all parties involved. This is to especially guarantee the peace-of-mind for the consumers who are voluntarily providing data and information and to be targeted for advertisements.
The shopping experience would be greatly augmented in several aspects, one of them being that with a universal and seamless rewards program, for one thing the inconvenience of having to carry around so many different coupons, membership cards and stamp cards will be virtually eliminated. Another aspect would be an advertising and promotional platform that is catered specifically to each and every individual. For example, you would be receiving promotions and discounts just in time for lunch at the places you usually frequent, and you'll be rewarded for your patronage with not just one but two types of tokens, so the layperson can really feel the difference in how much they are rewarded compared to any other loyalty programs out there in the market.
Many thanks for asking these questions and showing your interest in Carry, do let me know if you have anything else you'd like to inquire! :)