IPv4 is the zombie that won't die. Its address space has been exhausted for years, yet it still dominates the Internet. Still, it's giving ground at a rapid rate, and IPv6 support is becoming a necessity. For the foreseeable future, that means maintaining a dual stack. Public websites, at least, can't give up the old protocol yet.
IP address management (IPAM) isn't a simple matter in a large network. It has to keep track of public addresses, network address translation, DNS connections, DHCP, and IPv6 addresses. Without a reliable set of IPAM tools, a network can waste address spaces, encounter address collisions, experience security weaknesses, and have poor resiliency.