HFT replaces massive floors of human traders doing basically the same job but at much lower cost. The competition between HFT firms for microseconds isn't parti

HFT replaces massive floors of human traders doing basically the same job but at much lower cost. The competition between HFT firms for microseconds isn't particularly useful to anyone else but what they do (reduce the spread between buying and selling and the price difference between markets) is useful to most market participants not planning to extract money from the market in the same way HFT firms do.