"The major benefit of HFT is it has improved market liquidity and removed bid-ask spreads that previously would have been too small." - Investopedia
"The size of the bid-ask spread from one asset to another differs mainly because of the difference in liquidity of each asset." - Investopedia
If the major benefit of HFT is improved market liquidity, and small bid-ask spreads are indicative of more liquidity, why are small bid-ask spreads removed?