You have a skewed perspective of what HFT is - Flash Boys probably contributed to this. That is a sensationalist novel and widely derided within the actual market making community. For example, fiber optic cables were outdated by microwave feeds several years before the book came out.
In fact, the most common form of HFT is low-latency market making, which directly increases liquidity and lowers spreads for market participants.
In fact, the most common form of HFT is low-latency market making, which directly increases liquidity and lowers spreads for market participants.