In California it is required by law technically, but I had no idea until recently and don’t know of anyone that does it. I’m honestly surprised because the shelter never once mentioned it was required and the vet hasn’t ever said anything either. The other great thing about it is that the license is supposed to match the microchip and license renewal requires rabies vaccination, so they can be used to quickly track bite records and in the event of an bite rabies vaccination can be avoided if it isn’t necessary.