Why must the spark from the spark plug occur at the correct moment relative to piston position (ignition timing), rather than at a random time?

1. So that combustion pressure builds and pushes the piston down at the most effective point in the power stroke, maximising performance and efficiency
2. Ignition timing has no measurable effect on engine performance
3. So that the exhaust valve opens earlier regardless of piston position
4. So that the battery charges faster regardless of engine speed