Why do you only get a spark from the coil when you turn the key off and on but not when starting?

The spark from the coil occurs when you turn the key off and on due to the sudden interruption of current, creating a voltage spike that can generate a spark. When starting the engine, the ignition system is designed to provide a steady current to keep the engine running, preventing the abrupt voltage change needed for a spark. Additionally, the ignition timing and conditions during starting may not be optimal for producing a spark. Therefore, you only see a spark when the key is toggled, which disrupts the current flow.