There are reasons why someone choose earth wire:

1. The neutral shared with the CCS earth wire
2. The neutral reversed with the CCS earth wire
3. The leakage caused a short circuit phase and CCS earth wire
4. The earth is not equipotential. If the CCS earth wire connects to the different places of the ground, that will cause a potential difference, which makes the CCS earthing wire live
5. The high-frequency interference, which will cause a short circuit of the phase line and the earth wire, brings the CCS ground wire with electricity.