its only a bull shit ceremonial role, last one was an x car salesman. Its the respect that having one provides.
It the past, it wasn't.
It was (and still is) important for an ambassador to know the attitudes and plans of the nation he is assigned to. That way, should anything arise, the state department simply ask the ambassador, "Do you think we can get Australia on board with this thing?".
The ambassador can then replay with an educated statement such as, "Absolutely, they'd get on board. They've been trying to get something like this done for the last 3 years." or "Absolutely not, they've been staunchly resisting this sort of thing for a decade."
But now we live in the age not of people elected to serve, but of megalomaniacs put in power by money who don't give a shit who dies or who they go to war with so long as they make their money for their masters.