even short haired dogs need grooming!
All dogs should be groomed, even at a simple level its a great bonding experience with dogs.
Short haired dogs continually grow new hairs and shed, they still have moult cycles like wild dogs (although artificial lights extending the hours of daylight throw their biological clocks out of kilter). But many, especially labradors with deep coats will build up dead hair under the outer guard hairs. Regular grooming will improve skin tone, and reduce somewhat the amount of hair shed into the house.
For long-haired dogs, grooming is vital.