Keyword terms are most common on advertisements in trains, where it wouldn't be polite to use your phone to scan a QR code (and difficult to do to because of the position of the ads). QR Codes are used most often on things you are given personally, such as flyers or coupons.
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I was under the impression that they were waning in Japan, with many newer ads simply encouraging people to "Google XYZ" to learn more.
Keyword terms are most common on advertisements in trains, where it wouldn't be polite to use your phone to scan a QR code (and difficult to do to because of the position of the ads). QR Codes are used most often on things you are given personally, such as flyers or coupons.