Several reasons.

1. I like mysteries. Over time I will give clues which may eventually lead to my identification.

2. Some of my supporters would not be happy if they knew how much time I was spending thinking about cryptocurrencies instead of chess.  When the time is right I will help them understand. All top tournaments have players from many countries. In many ways it would be easier for both prizes (and appearance fees/expenses which are sometimes paid in advance) to be paid in bitcoin instead of fiat.  I have a very good idea of the people I need to talk to in order to make this happen. How receptive they will be at this time is another question. They may not be ready for such a big change.