Having actual unique stable IPv6 addresses for every device is the dream of every Ad vendor - no need to bother with the huge array of tracking techniques and the chicken and mouse game of fighting various tracking protection solutions, just log the stable IPv6 of the user's device across any service they use.

So, of course, we then got Privacy Addresses, or whatever the name is. Which now means that you don't actually have a stable unique public IP, it actually changes all the time, and legitimate tracking and logging of your own network activity actually becomes much more complicated on IPv6.