I knew someone would come in with "liquidity".

Many HFT jump out when things get volatile, when liquidity is actually required.

Ultimately HFT is doing nothing of societal value, the race down to zero is never-ending and we are wasting huge amounts of resources on a totally pointless march towards zero. Exchanges should introduce random delays to allow market participants who really want to hedge / buy / sell, then we can shift some of the resources to the real world. The costs required to compete at the lowest latencies are large, and forcing small/medium players out the game, as the investment cost is large, which is also bad.

The system is hugely inefficient. The costs as latencies get lower are ever higher, for an extremely similar end result. The law of diminishing returns.