Their latency requirements are such that they want as straight and short a line as possible because a larger round-trip eats up precious nanoseconds. The speed of light is not fast enough for these folks
On that note, Ryan North's book "How to Take Over the World" has a whole chapter about this. He proposes building a tunnel from New York to Chicago, to get the best possible straight-line distance between the two cities, thereby minimizing latency. Leasing this line for HFT is the funding source for most of the later supervillain schemes.