With IPv4 you need an addres, a gateway, netmasks, DNS.
On v6, as long as you have a working router sending RADV packets, clients will self-configure via SLAAC. Granted, same with IPv4 and DHCP.
If you don't have a router, most things should work thanks to link-local+mDNS.
You can easily pop a second router on the network to bridge two LANs, no need to reconfigure the DHCP. Gateways self-advertise, etc.
The point I'm trying to make is that most people trying toconfigure their IPv4 network have a functional IPv6 network the moment they put the cables in (on Linuxes es at least, not sure about other platforms).