A high-frequency trader is essentially a thief.

At its core, it's about exploiting price discrepancies and system latency across platforms to siphon money — essentially, being a thief.

So what niche does a thief occupy? Why do thieves get to exist at all?

There are two possibilities.

The first is that he's stealing from other customers, but because his trading volume is so high, he pays the platform massive transaction fees every year. The platform turns a blind eye — it's basically a cut of the spoils. His existence may be neither rational nor legal, but since the platform benefits, it defaults to ignoring him rather than taking action.

The second is that he's stealing directly from the platform itself. Because he moves too fast, sometimes the platform can't even balance the books, and ultimately the platform ends up footing the bill. In that case, the platform will hunt him down worldwide — sue him, pursue him relentlessly, and try to recover its losses.

Under either scenario, making money isn't the priority. The #1 priority is the ability to clean up the mess.