You can replace the letters "HFT" in your comment with "any market maker" and come to exactly the same conclusion.
Liquidity has always, always been subsidized by "skimming". The rake market makers take from trades is the cost of liquidity: ie, of being able to buy shares immediately without getting shafted because the only orders on the market are from large traders who are holding out for very high prices.
Have you ever tried to sell a house? That's what crappy liquidity looks like: there are buyers and there are sellers, but nobody is anywhere near agreeing about the price of the goods being traded, and so it takes months to get in or out of a position, and you sometimes have to do it at extremely unfavorable prices.
Liquidity has always, always been subsidized by "skimming". The rake market makers take from trades is the cost of liquidity: ie, of being able to buy shares immediately without getting shafted because the only orders on the market are from large traders who are holding out for very high prices.
Have you ever tried to sell a house? That's what crappy liquidity looks like: there are buyers and there are sellers, but nobody is anywhere near agreeing about the price of the goods being traded, and so it takes months to get in or out of a position, and you sometimes have to do it at extremely unfavorable prices.