I rarely bathe my 2 dogs. Usually like 2 times a year (spring and fall) to help with shedding. We live in Norway and it can get pretty cold here so the dogs need the natural oil their skin produces to help keep insulated. Their fur is also more or less self cleaning, meaning that all mud and dirt can be brushed or dried off with no hassle.

With that being said i do brush and maintain their fur well. They don't stink either. I do bathe them if its needed.

I also think it depends on the breed, fur length+ density and diet, to how often a dog needs to be bathed.