SPACEX SCRUBBED THE STARSHIP LAUNCH YESTERDAY: “’Too many question marks about this flight and then we were 20 bar low on ground spin start pressure,’ SpaceX Chief Executive Elon Musk posted. ‘Best to destack, inspect both stages and try again in a day or two.'”

Absent some overriding urgency, you don’t want to launch in the face of known problems. In some ways, the worst outcome of that would be if everything still worked, because it would tend to make you sloppy in the future.