I can see where you're coming from, but it's important to remember that what they are competing on is not only time but also spreads. Spreads have tightened substantially over the past couple decades thanks to these firms [1], which means that the total amount to be made per trade has dropped significantly. On top of that, the landscape has become so competitive that trading firms are now purchasing order flow, which basically subsidizes broker commission fees for trading. This is a huge win for retail investors, as the cost of trading has made it much more accessible -- in the past you would have had to buy many more shares and make a much higher return to offset these additional costs of trading.

[1] https://awealthofcommonsense.com/2016/04/trading-costs-the-n...

I'm pretty sure that if you have lots of firms trying to be "1 microsecond faster", then that creates more liquidity than you would have otherwise.

https://www.modernmarketsinitiative.org/hft-provides-continu...

Note that the link looks like it's some kind of industry group, but the listed references look like a useful place to start if you want to read more

It's winner take all for whoever has the shortest path (for something like index arbitrage). There is no value added to anyone if another competitor invests millions in microwave relays or custom hardware parsing to snipe the previous low latency winner and beat them out. It's just wasted money, other than knock on effects of more demand for hardware growing the hardware industry faster.