I agree, jackets should be longer
I think it's just fashion, that's how other jackets are
I remember a travel show on PBS where the British guy was wearing a short jacket somewhere in Himalayas but all the locals wore longer coats
Or if you look at 1800s Western U.S. - they all wore long coats
I make my own, go most of the way down to knees, much better. EVent fabric isn't commonly available but there are other good WPB fabrics.