Doing it once is harrowing. Even doing it the tenth or the hundredth time might be harrowing. Doing it the thousandth time is starting to get old. Doing it th

Doing it once is harrowing. Even doing it the tenth or the hundredth time might be harrowing. Doing it the thousandth time is starting to get old. Doing it the ten thousandth time is business as usual. The place to improve from is not as good as you may think, "On the Demo-2 mission, NASA has estimated a 1-in-276 chance of losing the crew at some point." Once you have full re-usability, you can fly rockets several orders of magnitude more times. When you're flying that often, you have the ability to work out the kinks. If instead you limit to what today feels the safest, you might limit yourself from full re-usability and eventually being much safer. If you want to still go for full re-usability, adding a backup system might actually make things more dangerous: It's another thing that has failure modes. Redundancy can be a double edged sword.