Intuitively, you probably don’t want your trading orders to be read by someone else (especially if they could act as a counterparty), because if they know you’re a buyer, they can probably inch their offer up slightly and shave a bit of money out of your purchase. On any individual order, you probably won’t get taken for a ride — and maybe you’re even OK with that, since you get to make a trade for free. As long as your slippage cost is below $7 on your total order, maybe you even come out ahead. Even if you don’t particularly enjoy having your order info sent to a high frequency shop, Robinhood’s business model is resilient because when everyone gives up a little, no one is angry or incentivized enough to stop the process.

https://startupsventurecapital.com/robinhoods-exceptionally-clever-business-model-arbitraging-privacy-776663d4d855