Ask a few Robinhood users what the difference between a market order and a limit order is...

If a Robinhood user thinks they are getting the wrong prices when they buy or sell, then they should seriously contact the SEC because that is illegal (as far as I know the prices aren't wrong).

The reason guaranteed small-scale trade orders are valuable is because they are a way to avoid 'salami tactics' which involve slowly building up to a large order. By the end of a larger order the price will have moved, and the earlier 'sliced' traders will be disappointed.