I'd expect a cause is that most camera makers are Japanese, and it's not uncommon in Japan to uppercase words written in Latin alphabet for aesthetic reasons
Perhaps the combination of that and the old .raw filename extensions on old filesystem implementations where everything appears uppercase (since camera firmware is slower to catch up, this persisted for years even though contemporary OS already had no such limitation) made it stick.
Very plausible, I haven’t considered it.
Perhaps the combination of that and the old .raw filename extensions on old filesystem implementations where everything appears uppercase (since camera firmware is slower to catch up, this persisted for years even though contemporary OS already had no such limitation) made it stick.