Animals do deserve to have it good. First, their basic needs like food and water should be taken care of. Then self-fulfillment and medical care. After that, higher philosophical concerns such as freedom from government registration.
But that's in general. Specifically, registering indoor pets does nothing to prevent pets from being abused. What it does is satisfy the state's innate desire to assert control, and create a fakejob for a bureaucrat to administer the registration.
In Seattle, the real reason is to collect fees to run the Seattle animal shelter and animal control. I appreciate knowing that if somehow my cat gets out someone could return him to the animal shelter where they'll scan him chip and contact me.
But that's in general. Specifically, registering indoor pets does nothing to prevent pets from being abused. What it does is satisfy the state's innate desire to assert control, and create a fakejob for a bureaucrat to administer the registration.