It looks like that because it's complex and technical and people don't understand it, but it also saved retail investors a bunch of money. I don't understand how a jet engine works, but I don't feel any urge to advocate for jet engine policy changes.
For those who don't understand your comment about HFT saving money for retail investors, several well-regarded published studies suggest that the narrowing of mean bid-offer spreads since the introduction of HFT can be attributed to HFT.
There are actually a variety of HFT strategies, but there's good evidence that the high-speed market-making variety are good for small volume investors. Those in favor of getting rid of HFT should be specific about exactly which sorts of HFT they want to ban.
The narrowing of mean bid-offer spreads isn't surprising, since many HFT strategies are essentially faster versions of traditional market making. They're able to offer narrower spreads (better prices) than traditional market makers because they're faster at widening spreads (worsening prices) when the market starts to move in one direction. On average, this means better prices for people trading small amounts of stock. However, for large institutions that trade market-moving volumes, low-latency market making means worse prices, since the market makers are faster at noticing and widening spreads when there are large market-moving trades afoot.
Also, the ETF arbitrage variety of HFT strategies reduce the amount that ETF prices differ from the prices of the individual stocks within them. This results in fairer prices for people who primarily invest in ETFs.
On the other hand, low-latency market-making results in less liquidity being offered when the markets are moving quickly in one direction, which is when it's most important to have liquidity.
Also, for the average person, a very large portion of their exposure to the stock markets is through pension funds and mutual funds, which tend to make the sorts of large-volume market-moving trades that are hurt by HFT's ability to notice and quickly get out of the way to avoid being run over.
Disclosure: I've never worked for an HFT fund, but I do work in the financial services sector. I did some work on systems designed to reduce market impact of large institutional trades, part of which is breaking up patterns so that HFTs are worse at noticing and widening their spreads.
