I always thought zettai ryouiki in winter setting defeats the purpose of wearing warm winter jacket.
I mean this picture still is amazing, just sharing an opinion.
To Japanese girls, fashion can trump good sense. This goes double for anime girls who can't actually get cold.
That said, it's like saying that there's no point in wearing a coat if you aren't wearing a ski mask to cover your face; Covering part of your body in extra warm clothes so that you don't lose heat out of one part of your body can make up for doing nothing to prevent heat loss out of another part. Wearing a coat over shorts is still better than wearing nothing but short sleeves and shorts, after all. (Also, the legs lose a lot less heat than the head or torso.)