Yes I am aware of that. Not in service yet which makes my point. They are still decades away from autonomous ships. Aircraft with passengers, possibly never.
One other thought, crew costs are about 13-15% of aircraft operating costs. Surely cabin crew would go first? The argument being there are no staff on a train or bus to show you where the exits are so why do you need them on an aeroplane? Replace them with a vending machine?
These are not my thoughts by the way. Just floating the business argument.