"But the power process is just a game, or perhaps more accurately a built in biological addiction to games that caused us to pass on our genes in the past. Why is it truly metaphysically better than, say, racking up Reddit karma?" Because it gives us psychological fulfilment. We are conditioned through millions of years of evolution to find it psychologically fulfilling. That's the point. His argument is that living a life that may be less physically secure, but psychologically fulfilling is a better life to live. That's why it's better.