I think you are letting your "speculation is bad" bias interfere with your understanding of dynamical systems.

When I press the buy and sell button, I want the transaction to happen as quickly as possible. So does everyone else.

My millionth of a second is different than yours, and everyone else’s.

It is no different than buying or selling anything else. And there is no loss from the additional liquidity, you can easily set a limit at which you want to buy or sell.