Tom Scott did a nice video [1] on IEX's setup with 38 miles of fiber to add enough latency as a mechanism of fairness. Purportedly, this benefits all exchanges after it was successfully deployed. It seems like the incentives are not there for larger, more established exchanges to implement such blanket latency. So, firms like GS see a benefit to this kind of investment.

[1] https://www.youtube.com/watch?v=d8BcCLLX4N4