If you have a 401K or own shares in a mutual share, you should care about it.
The HFT algos siphon off billions every year from the big, slow "dumb money" large institutional investors (e.g. pension funds, index funds, insurance companies).
For example, if an insurance company needs to liquidate its portfolio to pay a claim, the HFT will sense the insurance company placing an order in the market and try to skim 5-10 cents per share by manipulating the share price during the trade. Its a zero-sum game.
The insurance company lost and the algo won. Market markets exist to provide liquidity (match buyers and sellers), not to front-run and bid up orders from customers.