Stateless autoconfig is, but stateless is bad for ISPs and network administrators because it means anyone will be able to get an IP just by plugging their machine into the network. With only 3.40282367 × 10^38 IPs available, you can see why they would want to ration them.
At current population growth, we will run out of addresses—if we give every human one IPv6 address—in only ~6000 years, or—if everybody should get 1000 addresses, for all those internet-enabled toasters and such—in ~5500 years. Obviously we already need to plan ahead and carrier-NAT IPv6.
according to node-requirements rfc-4294, dhcpv6 is infact optinal. however, for an enterprise network, the fact that any v6 capable device can get a legit address is probably not such a good idea (it can be argued the other way also ofcourse).
