Imagine buying a lottery ticket from me. I run the lottery. I print it out, look at it, oooh, you know what, I can't sell you this one. Of course you don't need to pay. Goodbye. Did you lose money?
Scenario 1: 1. Client buys share for $400 2. Hedge funds get short squeezed (because trading is not restricted by Robinhood) 3. Stock shoots up to $1000. Client made $600
Scenario 2: 1. Client buys share for $400 2. Robinhood restricts buying the shares (so the short squeeze doesn't happen) 3. Shares plunge to $50 because the short squeeze failed to happen (ie the hedge fund did not have to purchase the shares at higher prices, which is where the capital that the traders would share amongst themselves would come from) 4. Client lost $350