As a practical matter any organization that tries to do things with other organizations needs to have some party that can act on its behalf. That is why Ambassadors are necessary.
The current constitution of the IETF means that the chairs of the IAB and the IETF have very limited authority to speak for the organization, but of course they have to.
I have argued for junking the DARPA constitution for years. It was designed to keep power in the hands of the few while the rest of the organization didn't worry their pretty heads about it. They don't even get to call themselves members.
We should junk the noncon completely and the constituency currently qualified to stand for noncon should elect the chair.