Why would a national leader need to travel in luxury? A fine argument can be made that they need to fly first class in an airliner, and stay in a business class suite.
Deal with the world they foist upon all of us. Bastards every one.
All other arguments aside, I do have a real problem with that argument.
Up until 2001, Australian Prime Ministers generally flew commercially on Qantas to travel overseas - yes, in first class, but on normal scheduled flights.
Today they travel on a RAAF operated Boeing Business Jet set up for VIP transport.
Why the change? September 11, 2001. Prime Minister John Howard was in the US that day - in Washington DC, specifically - for commemorations of the fiftieth anniversary of the signing of the ANZUS Treaty. He wound up being trapped in America because of the grounding of all commercial passenger flights. Eventually the US Air Force flew him home on one of your VIP planes.
It was not a good situation from a security or governance situation. Our Prime Minister was out of the country and we had no direct control of getting him home.
I think the planes at least are a genuine security requirement in the modern world.