In my experience, it is helpful to be able to remember IP addresses instead of just urls. Not a dealbreaker, but useful in some cases. Example - I set up a VPS server as a testbed/development server/socks proxy, but didn't bother to register a domain with it. It would suck to look it up the long IPv6 address the whenever I connect to it on a new device, or try to show it to someone else. The ten digit IPv4 address is fairly easy to memorize in comparison.