There are several reasons for Bitcoin's inventor to keep his identity anonymous. One of them is privacy. As Bitcoin gains popularity and becomes a worldwide phenomenon, Satoshi Nakamoto; it will likely be in the limelight of the media and governments. Another reason could be Bitcoin's potential to cause a major disruption to existing banking and money systems. If Bitcoin is massively adopted, its strength could exceed the official currencies of the sovereign nations. This threat to existing currencies could result in governments taking legal action against Bitcoin's creator. The other reason is security. Looking at 2009 alone, 32,489 blocks were mined. The reward was awarded 50 BTC per block, and the total payout in 2009 was 1,624,500 BTC. This amount was worth $ 13.9 billion as of October 25, 2019. It can be concluded that until 2009 only Satoshi, and perhaps a limited number of others, were mining and sharing this reward. Someone who owns this much Bitcoin could become a target of criminals. Especially since bitcoins are not like stocks and are similar to cash, where the private keys needed to confirm spending can be printed (literally kept under the pillow) ... Even though Bitcoin's inventor will likely take measures to trace extortion transfers, using a pseudonym is a good way to limit Satoshi’s exposure to extortion.