People are so used to seeing dog food in tins, pouches and sachets that it often does not occur to them that it can come frozen. This has a number of conveniences, not just for your dog, but for you as well.
Why freeze dog food? First of all, frozen food does not need any kind of preservative in order to keep it fresh. This means that there is no need to preserve the food in jelly or biscuit form: you can feed your dog high-quality, fresh meat tailored to their nutritional needs. Frozen food also can contain plenty of natural meat juices and blood. While this may make some people squeamish, for dogs it is a delicious treat. It is also one of the ways dogs in the wild would stay hydrated, so your dog will not need to gulp down gallons of water every day.
Frozen food is not cooked like most standard dog foods. Cooking food removes a lot of its nutrients, and alters the levels of others. This makes it blander and less healthy than frozen food, which is raw and so contains all the nutritional goodness of fresh meat in the wild.
Finally, frozen dog food is easier for you. This is especially true if you are feeding your dog in accordance with the BARF diet. Rather than planning out meals full of fresh meat, you can just feed your dog a portion of frozen dog food. All you need to do is defrost it, and your dog's dinner is ready to eat.