"Stateful" autoconfiguration, is often used when is needed a more rigorous control about the address allocated to hosts, on the contrary of "stateless" autoconfiguration (of which only worry is that the address wasn't duplicated).

So, depending on the network administrator politics, it could be required that some addresses were allocated in a permanent way to specific machines, consequently the "stateful" mechanism is required, but the control of the remaining parameters could be not so rigorous.

Of course, the politics can be opposite to the exposed above, that is, the case in which it has no importance the allocated address, and consequently the "stateless" mechanism is used, but it is desired that remaining parameters were allocated in a "static" way, with information stored in a server.