Although dogs and cats are naturally good and keeping clean by licking or "self grooming" we still need to groom them professionally, especially dogs, to ensure healthy coat, skin, smell and general clean appearance.
Short coat dogs should be groomed once a week.
Curly Coats, because waterproof in nature, needs to be not only bathed but clipped.
Wiry coats IE: dense coats needs grooming everyday.
Silky coats needs daily grooming.
Smooth coats require weekly grooming.