I would agree with the fact that those 3 types of dogs definitely might need a little help retaining their body core temperatures. I would however respectfully disagree that those are not the ONLY ones who would need a little help.
I think if people would employ more common sense with their pets we would see far fewer weather related injuries in veterinary clinics. If you are cold outside it is not necessarily true that your dog will be cold also BUT we must consider the feet which are bare on the bottom and can become frostbitten very quickly. This is also true in regards to the ears.
Our tiny, sick and elderly fur babies definitely need special attention in extreme weather conditions. Don't assume that just because our babies do not fall into those categories that they don't need the extra attention as well.
Better safe than sorry. Today's weather forecast in My City, Indiana is 28 today and 6 overnight with a few more inches of snow. I tell you this as I gaze at my German Shepherd snoozing lazily in front of my wood burning stove, sporting her awesome little sweater that keeps her toasty warm! I'm totally jealous!