What the heck is going on with Londoners wearing shorts in icy temperatures?

I don’t own a winter coat. I walk about mostly in a sporty / cotton vest all year round with either shorts or 3/4 length bottoms with temps as low as 5 degrees. If there’s a northerly or easterly wind that lowers winter ‘feel’ temps to 0, then I whip out my no lining rain coat or summer denim jacket and wrist warmers (the only part of my body that feels cold below 5 degrees C). I never use scarves ‘cos my upper body generates heat like crazy. I have a slim athletic build, thankfully my muscles and type of food I eat keep me feeling toasty on the inside. Anything about 5 degrees begins to feel warm to me, and the thought alone of putting on a coat of any kind makes me sweat 😅 I get quizzical stares, I’m used to it and feel the same about people wearing coats, gloves and scarves when it feels warm (to me!).