One of my colleagues asked me why a DHCPv6 client on a router interface will not get a default route installed. This because DHCP client for IPv6 was initially intended to get a default route just on end hosts and not on nodes. And still we had SLAAC to provide necessary default route on the RA receiving side:
interface ethernet 0/0
ipv6 address autoconfig default
And we will have a default route pointing to the next hop Link Local address.
R1# <strong>show ipv6 route</strong>
ND ::/0 [2/0]
via FE80::A8BB:CCFF:FE00:200, Ethernet0/0
Later on, some ISP wanted to use a single centralized protocol instead of SLAAC on between access nodes and distribution, so they asked IETF to include support for default routes in DHCP. And then this draft was published. In the meanwhile 6RD became also popular, where each CPE is preconfigured with statically well known relays as default next hop. But I am sure that eventually someone will need a way to inject default route in a v6 only environment, and therefore this feature will need to be available (please update me if I have stale information)