Imagine the advantages of having a dog which is easily handled.
Grooming is easier.
Grooming a dog which stands nicely is a pleasure.  The job can be done quickly and thoroughly and you can easily reach all the awkward parts that could easily become matted.  To groom a dog which will not stand still can be a nightmare and could get to be a spiralling problem.  If the dog will not let you remove a small mat from his coat, it stands the risk of being left.  The mat can only get worse and if he would not let you remove a small mat, what chance do you stand with a filthy knot of hair?

Daily grooming sessions will help you to build a good relationship with your dog.  As pack leader, it is your right to pick the time and place for these sessions. If they are enjoyable for the dog, it will help to establish your position as top of the pile.  If there is a running battle every time the brush comes out, your relationship with the dog could be in a very unstable state.

It is essential to groom a dog coats to remove dead hair, but the most important reason is to build and reinforce the right relationship with your dog. There is more to grooming than simply brushing the coat, it includes having the dog stand still while you wipe clean muddy paws or towel them down after a good romp.  Teaching your pup to stand still now could save you a chase around the sofa with a filthy muddy hound.

Visits to the vet are less stressful for everyone. 
For a dog that is difficult to handle, a trip to the vets can be a nightmare for them, the owner and the vet.  The dog must be examined for an accurate diagnosis and treatment to be given, but this is rather difficult to do when the dog is doing a wall of death act around the consulting room.  For the dog who behaves badly at the vet, each visit can become worse than the last.  They know as soon as the car pulls up at the surgery where they are and react accordingly.  They are already in a stressed state before the vet even sees them and are immediately on the defensive when anyone tries to handle them.  This situation would never happen if all puppies learned to accept being handled and to trust in humans without question.
Giving medication is straightforward.
Few dogs go through life without needing some sort of treatment, such as tablets, bandages or ear drops.  This can be a real problem if the dog will not accept their owner's attention, the condition will not get better if not medicated correctly, and it can become costly if your dog must be taken to the vet to administer medication, it does not lead to a happy relationship if a battle ensues every time a simple worming table is being administered.
A well handled puppy makes for a well socialised dog.
No matter where you go, you will always meet people who do not know the correct way to approach a dog.  Children can be prone to reach out to the dog first and ask questions later, some adults insist on giving dogs a well meaning pat on the top of the head.   For a dog which has not become used to being handled, these situations can be very difficult to deal with and they may react badly with a growl or a snap.  Not really considered acceptable behaviour, whatever the dog's reasons.
Dealing with difficult situations.
Should a difficult situation arise, will your dog trust you enough to allow you to help them.  They could get their leg trapped in a fence, get a thorn stuck in their pad or fall down a hole that they cannot climb out of and need your help, but if they will not let you handle them when they are not hurt or distressed, what chance do you have when they are.
Stroking a dog is good for you.
Last but not least, stroking a dog is one of life's pleasures and is a great stress buster.  So for your own health as well as theirs, teach your puppy to enjoy being handled by grooming them, stroke them and build up the relationship that having a dog is all about.
Daily health checks.
Regular grooming and handling sessions are an excellent opportunity for you to give your pup an all over health check. It is useful to get into a regular routine so that nothing is missed. This should be a pleasant and relaxing event for you both, but not a game.  Choose your time carefully, ideally when the pup has finished with wild games and is feeling sleepy and ready for a cuddle.  Talk to them soothingly and reward them with verbal praise for accepting your handling.  Do not allow them to turn the handling session into playtime by stealing the brushes and running off with them.  A dog which is all wriggly is as difficult to handle as one which is trying to bite you.