Yes: it put a much larger, more expensive, and less efficient part of wall street out of business. Before it was done with computers, it was done with lots of people doing the same job. What was that job? Well, if you want to go to a market and sell something, you generally would like for there to be someone there who's buying it. But it's not always the case that there's a buyer there right at the time who actually wants the item for their own use. The inverse is also true for a prospective buyer. Enter middle-men or market makers who just hang around the marketplace, learning roughly how much people will buy or sell a given good for, and buy it for slightly less than they can sell it later for. This is actually generally useful if you just want to buy or sell something.
Now, does this need to get towards milli-seconds or nano-seconds? No, this is just the equivalent of many of these middle-men racing to give you an offer. But it's (part of) how they compete with each other, and as they do so they squeeze the margins of the industry as a whole: In fact the profits of HFT firms have decreased as a percentage of the overall market and in absolute terms after the initial peak as they displaced the day traders doing the same thing.
> it's not always the case that there's a buyer there right at the time
This hits the nail on the head. For a trade to happen, counterparties need to meet in price and in time. A market place is useless if there is nobody around to buy or sell at the same time you do.
The core service market makers provide is not liquidity. It's immediacy: they offer (put up) liquidity in order to capture trades, but the value proposition for other traders - and the exchanges! - is that there is someone to take the other side of a trade when a non-MM entity wants to buy or sell instruments.
It took me a long time to understand what the difference is. And in order to make sure that there is sufficient liquidity in place, exchanges set up both contractual requirements and incentive structures for their market makers.
Now, does this need to get towards milli-seconds or nano-seconds? No, this is just the equivalent of many of these middle-men racing to give you an offer. But it's (part of) how they compete with each other, and as they do so they squeeze the margins of the industry as a whole: In fact the profits of HFT firms have decreased as a percentage of the overall market and in absolute terms after the initial peak as they displaced the day traders doing the same thing.