[freeone3000]

They don't do this. See https://nypost.com/2020/12/17/sec-slaps-robinhood-app-with-6... .

[QuesnayJr]

But they can. That's why they got into legal trouble with the SEC. See page 4 on the actual SEC document on the case, the section called "Best Execution": https://www.sec.gov/litigation/admin/2020/33-10906.pdf