The compulsory standards for safety requirements of domestic equipment are not high, or there is no corresponding standard certification, such as CE of the European Union. Safety relays are used when there is a risk of personal injury or property damage. It does not enter the PLC, but uses a hardware method to disconnect the power supply, so that the device is in a state of complete shutdown; and the safety relay itself also has several contacts to ensure that it can be effectively disconnected when a fault occurs. If your equipment wants to enter other countries, at least have CE certification, then there will be problems in this regard. Therefore, some equipment that needs to be exported, especially the EU and Japan, is usually equipped with safety relays.
Of course, with the increasing emphasis on safety in China, some technical standards and implementation will gradually be in line with the world. In the 13th Five-Year Plan for safety-related standardization work, it is mentioned that the updates and upgrades of machinery safety-related standards and strengthened implementation, and the requirements related to the design of safety circuits will become more and more strict.