I know some people don't see these as benefits (compared to "useful products like smartphones"), but we do cause instrument pricing to be more accurate and a thinner buy/sell spread and greatly increase liquidity.
But it would be interesting to see some quantitative data on the effect.
Increasing volatility and enabling fast algorithmic trading may not be good things overall, even if some traders benefit.
And as I noted, if you care about fairness in an online game, usually you try to remove the penalty effects from long ping times (or the bonus effects from short ping.)