[logfromblammo]

It isn't just about time. If someone knows what you are willing to pay, they can engineer their trades such that you pay exactly that. When the system itself is not paid unless you pay less than you were willing to pay, there is a built in incentive to not reveal that information to potential middlemen.

In that context, trade speed doesn't matter. If arbitrageurs cannot profit by breaking your trade up into two trades with themselves as middleman, it doesn't matter how fast they are.

Aside from that, any system where trades can occur faster than information can enter your eyeball, process in the brain, and shoot down your arm to click a mouse button is one that unfairly disadvantages the unaugmented human participant.