I totally agree, it is not strange at all. It is just typical of the way we are sometimes regarded, albeit by a minority, as freight rather than paying customers. As you say, they can put a jumper on as many other crews on other airlines do. But some seem to prefer to turn the temperature up and hang around the galleys with the cabin an oven and the galley at a comfortable shirt sleeve temperature.
I can't remember the last time I needed to use a duvet in F or Club and still wake up uncomfortably hot.