Millions of birds live in freezing temps and in other various less than ideal circumstances in the wild.
Not all breeds are created equal, there are many birds that simply can not and will not survive extreme cold or even extreme heat... Chickens is a generic term that covers many different breeds, some far more capable of handing the cold then others while some are far better at handling the heat... And that is just chickens, some of us keep other birds in our coops...
The short of it there is no one size fits all coop design, appropriate for all breeds in all climates...