What are the reasons why some companies master the core technology but don't apply for patents?

The real core technology has not been revealed. Patents will give a company a technological monopoly advantage, and at the same time, the core technology will be secretly protected through corresponding application and writing strategies. The risk is technology leakage or the loss of key personnel. The risk is actually more important, that is, competitors have figured out the secret after seeing your patent, and then it is time to apply for a patent in secret.