Another level of "Why": QR codes were invented in 1994 in Japan for automated scanning. As you all probably know, Japanese uses Kanji, and hiragana+katakana; it

Another level of "Why": QR codes were invented in 1994 in Japan for automated scanning. As you all probably know, Japanese uses Kanji, and hiragana+katakana; it does not rely on the Latin alphabet. However, Japanese speakers are familiar with it and occasionally use it for specific purposes. While katakana is commonly used for transliterating foreign words, sometimes the exact original spelling is preserved for stylistic reasons, especially in acronyms or single-word cases. However, in such cases, they usually use only capital letters. In Japanese, there's no distinction between lowercase and uppercase letters. So for them this distinction is, if you allow some leeway, similar to the differences between normal, italic, or bold letters in English. So it makes sense with this context, if you are making a "group of letters and numbers", to default to uppercase + numbers as the normal/shorter version.