If you take out MM trading, retail gets cheated.
Remember that MM's trade with each other, and settle at the end of the day. You can equate it to you and a friend playing with monopoly money, when you were younger. At the end of the day, you go back to "square", that is where they settle, Along the way, they force buyers in and out, depends which way they want to tag them along. The bad news for the individual investor is that this is not monopoly money. Don't buy more that you can afford to hold, meaning don't get a margin call and be forced to sell; been there, done that.