Why do People dress Dogs?

Dogs have been around on the planet for thousands, if not tens of thousands, of years and are all obviously descended originally from wild animals. During all this time they have managed quite well with the hair they were given and I find it odd that people now want to dress them in large or small dog jackets. In some ways I can understand it in a few situations, where people live in an extremely cold country for example or for hairless dogs, but for the majority of cases I don’t really see the point. For most people it would appear to be a fashion statement, but why can’t they do this with their own fashion rather than including the dog. Dogs have hair to keep them warm and in most cases this is more than adequate and a jacket is not really required. I also think it looks a bit odd and that most dogs look pretty cool as they are and don’t really need a jacket to enhance that.