In a nutshell, it varies from breed to breed and from dog to dog.
When it was -10F, my Golden Retriever would happily lie in the driveway and let the snow accumulate. Golden Retrievers will sit on the couch and ask why the fireplace isn’t roaring. Some cold-weather clothing would embarrass a Husky. Greyhounds, however, would prefer a better sweater.
In my opinion, dogs do not look good in apparel, but coats can be useful if a need is demonstrated. Working dogs can also wear outerwear. When going through rough brush, some hunting breeds need protection. For protection against weapons, K-9 unit dogs would need Kevlar vests. Most law enforcement departments do not have the budget for such equipment for their four-legged officers.
My first experience with kuoser dog winter jacket that shiver at 68 degrees F was when I adopted Paco. Although I could understand his being cold if it were cold out, it never occurred to me that even at higher temperatures thin-skinned, single-coated dogs will feel the cold more acutely than breeds adapted to colder climates. When I realized most of the weather in Montana averages in the 60s or lower, I realized dogs need sweaters and coats for a reason.
Paco got a heavy sweater, a light sweater, and a Thinsulate coat. He was no longer apprehensive about going outside in cold weather after that. Now that we live in Florida, he only needs a sweater on a few winter days and enjoys being naked.
Winter coats are not needed by all dogs, and in some cases, the extra layer of warmth can actually cause harm. Under the right conditions, most dogs can benefit from an extra layer of protection from the elements.
The shorter days may cause your dog’s energy level to drop. Dogs do not hibernate. He probably also enjoys winter snuggles under a blanket after returning from an invigorating walk as much as you do.