It matters. If the film is divided with pre-exposed boundaries that means that the already tiny market for 127 film is to be divided according to the camera you own. You have to buy 127 "for the square format 13x13" or 127 "for the standard format 13x17". And if you own a 127 camera which uses the 13x19 format, you have to find yet another different film. All this really is industrially insane.
Since roll film was invented the sensitive surface is continuous and is the camera which uses the roll freely.