Why would you expect your code to compile and run correctly on the first try? Same energy. They can test / simulate as much as they want on the ground but the

Why would you expect your code to compile and run correctly on the first try? Same energy. They can test / simulate as much as they want on the ground but the first full launch is bound to reveal issues. Best case those issues just stop it from reaching the desired level of performance, more realistically they mean it goes boom at some point.