Earlier quoted context omitted.
We’ve been launching airplanes with steam catapults for many decades, albeit in an environment where we’re willing to take more risks than to go see Grandma, but many of the catapult concerns are areas where we have decades of experience and hundreds of thousands of successful cat shots.
But the catapult isn't for saving on energy that needs to be carried on the aircraft. It's simply that you can't build engines and propulsion systems on a plane with the desired takeoff weight when you have as short a runway as you do on an aircraft carrier
Regardless of the underlying driver to implement it, we've solved some of the concerns that GP mentions for ground-assist launches, so there is a body of experience/work we can easily build upon.