Its because each passing day, AI is becoming smarter and smarter. Google's deep mind defeated one of the finest player in alpha go (Ancient Chinese game, It has billion billion possible combinations). Elon's open AI defeated top player in Dota. If the trend continues, a time will come when AI will surpass human intelligence and from that point onwards, we will not be able to understand what AI is doing or building around us. To prevent this we must understand what AI is doing so Elon proposed an embedding layer of advance computing around brain to make humans smarter. This sounds logical.