[homie]

Mostly because it’s impossible to accurately predict the market - and this is just a competition to see who can build the best model.

[thegjp210]

HFT firms aren't trying to predict "the market" as a whole - just small eddies of it. A typical example of this is arbing names at the bottom of index fund rebalances. Speed is important mostly to make sure someone else doesn't hit the arb first.