For humans to have any reasonable presence somewhere else in our solar system (moon, mars, etc.) we need the ability to launch tons (literally tons) of stuff to orbit and to the destination. and we need to launch it often to do anything in a reasonable amount of time. the only way to do that is to make reusable launch systems. SpaceX's Falcon 9 has aced that for satellites (see Starlink and everything else they've launched). The Starship launch system is capable of launching a significantly larger payload, ~20 times more. What they demonstrated yesterday is that a launch system that is capable of getting us anywhere in the solar system can be reusable. Huge accomplishment.
