Root Cause matters because release quality is the gap between local proof and live proof under real traffic. It gives builders a precise word for the thing they are changing, debugging, reviewing, or shipping.
ELI5
Think of Root Cause as a checklist or dashboard for keeping the app alive. It gives one small job a clear name so the whole app is easier to understand.
In practice
Use it to separate local success, preview success, production success, and revenue-critical success. In practice, name the owner, input, output, failure mode, and proof before relying on Root Cause.