Advertisers do not need to rely on the UDID(which is still widely used) to track you since all that matters is they have a unique key they can associate with th

Advertisers do not need to rely on the UDID(which is still widely used) to track you since all that matters is they have a unique key they can associate with the hardware. The MAC address does the same thing and there are a handful of other options that are close enough for what they care about.