what does dog grooming do to your dog?

i have 2 weiner dogs. and they have a bad case of fleas. i give them baths but the fleas don’t go away though. so i was thinking about asking my mom to get my dogs groomed. but does dog grooming get rid of fleas? like completely? what else does dog grooming do to help your dog? thanks
by the way, they’re outdoor dogs. they never come in the house cuz my mom doesnt allow it.