Children, like adults, have different tolerances for heat and cold and, in the vast majority of cases, the mother or father will be perfectly well aware of what those tolerances are. I don't for one minute believe that the world is full of people thinking "Ooh it's cold, puffa jacket and wellies for me, shorts and sandals for the DC." If these people do exist then they don't seem to live round my way.
My 17 month old is showing signs of taking after his father and refusing to accept that it might be even a teeny bit chilly until we have polar bears trekking through the garden. I, on the other hand, despite being a hardy northerner, spend the entire winter in a quest for warmth. I have been known to stand inappropriately close to strangers at bus-stops just because they looked warm.
We use a wrap sling full-time. I have only used a snowsuit twice with the wrap and we were both wringing wet within 15 minutes. In this cold weather he wears jeans,a long sleeve top and a fleece over it, a hat and his normal socks and shoes. He won't wear mittens - he rips them off with his teeth and throws them away. He regularly takes his hat off. We have the dreaded gap between trousers and socks and if I try to put my arms around his legs to cover it he chunters at me and pushes my arms away. If his hands get cold he shoves them down my back. If he wants his hat back on then he bashes me on the he bashes me on the head with it. He has never shown any signs of being cold. The shared body heat advantage is huge. Even I, cold-blooded as I am, don't wear a coat when I am slinging him in the winter as I get too hot. I just wear a wooly hooded top and occasionally a pair of arm warmers. I don't wear a scarf or anything like that. No doubt we are one of the mum and baby combos who have been judged spotted by MNetters.
For what it's worth, the Innuit women carry their babies in pouches sewn into the back of their coats. I think it is probably colder there....