A dog license is issued by local governing bodies to people who own dogs. Pet registration helps municipal authorities keep track of the pet population. It also ensures that all pets in that locality are vaccinated against diseases such as rabies, leptospirosis, etc. which is a requirement for registration.
For pet parents, the dog license establishes the ownership of the dog, which can be crucial in case of disputes or if your dog gets lost or stolen. In case of a dog-bite, the municipal authorities have the legal authority to take your dog away, if they are not registered. Since the dog license is legal proof of your dog being vaccinated against infectious diseases such as rabies, there may be leniency shown in terms of repercussions for the dog owner.