Certainly support for the GUID field type itself is most important. As for the generators, though they are non-essential, they are very useful. Other platforms and libraries have standardized on uuid generators, so I don't see why PostgreSQL can't.
Maybe I am oblivious to the reason, but why is there a need for a special data type for GUID/UUIDs? Wouldn't you always be doing an "equality" anyways? Wouldn't a varchar suffice?