They are not real spreads. They are fake spreads made by HFT bots using small orders. Once a real investor will try to execute on such an order, the HFT bot wil

They are not real spreads. They are fake spreads made by HFT bots using small orders. Once a real investor will try to execute on such an order, the HFT bot will either withdraw it (or it will simply get filled because it's a minimum order for the minimum allowed amount), and then the bot will immedately put in another order which will make more money for the HFT and less money for the investor. HFTs will use their fast connections to other markets to make sure that the new order is such that the investor will have no choice but to pay the price, because by the time the investor will try to go to another market to execute the trade cheaper, HFTs will already have been on that other market have front-runned the investor's order. This is not "providing liquidity". This is parasitic behavior. Not all HFT strategies do this, but many do.