The shuttle program was killed by costs. Keeping it flying safely was really expensive. Despite the safety record you mention, it was the best approximation of

The shuttle program was killed by costs. Keeping it flying safely was really expensive. Despite the safety record you mention, it was the best approximation of a spaceship that we, as a human species, ever created. A spaceship program is something you either fully commit to by spending billions on it, or you abandon it. Nevertheless, there has been nothing that has come close to it since.