If you don't like it, try to convince regulators that it shouldn't be legal and provide a framework for criminalizing/fining it without unintended consequences, and then find a way to pay regulators more in bribes than the HFT shops do, even though their pockets are deeper than yours, and then things may change.
If that sounds impossible, that's another answer to your question
Because it's legal and profitable.
If you don't like it, try to convince regulators that it shouldn't be legal and provide a framework for criminalizing/fining it without unintended consequences, and then find a way to pay regulators more in bribes than the HFT shops do, even though their pockets are deeper than yours, and then things may change.
If that sounds impossible, that's another answer to your question