Main difference there being that switching cities means probably switching ISPs. You can absolutely carry over your IP address when you move between the same provider, if that’s part of your service plan, and that may well happen with some ISPs even without it being part of your plan. There just isn’t really much of a need for people to carry a static IP, except for some businesses, and I’d say the main reason is that people don’t visit websites by memorizing and typing in an IP. They do memorize and type in phone numbers.