Assume that SpaceX Starship cannot land safely with passengers on board. That means it can't be used for high-speed intercontinental travel.

For space travel, Starship could launch on a Super Heavy Booster, as is the current plan stated in Wikipedia. Additional Super Heavy Boosters could carry fuel, Lunar landers, and landers & ascent modules for any other destination in the solar system. Landers would have to detach from the Super Heavy Booster, and dock with, the Starship during, or after the Super Heavy Booster re-fuels the Starship. Falcon 9's would carry Crew Dragon capsules from Earth, to rendezvous, and dock with, with the Starship, after everything else is done. Starship would simply provide a larger habitat and propulsion system for whatever the destination & return mission happens to be. It would never actually land anywhere, unless it was unmanned.

With this configuration providing alternate means for landing astronauts to the Earth's surface, or Moon's surface, the Starship might be safer for human spaceflight, and would not be required to land on Earth, Moon, or any other planet/moon.

Obviously, SpaceX does not have to do anything that I suggest. It's their business.