Yeah on second thought I could be wrong about Robinhood, it's only a theory that they're directly trading against their customers, that would explain why they don't allow any cash BTC withdrawals.
As for guys like Binance, FTX, or even more obvious guys like Houbi, they operate exactly as bucket shops. Real exchanges can't legally participate in trades against exchange member, since that'd display a clear conflict of interest.
Yet this is exactly what bucket shops do, like Binance and co. They offer enough leveraged OTC derivatives that are not necessarily fungible, trade against clients, and make their own markets/prices so they can pick them off easily with seemingly legit margin calls.
It's the same business model as most CFD, Forex shops.
And real trades on legitimate exchange are guaranteed, verified by clearing firms. This is so no funny business such as "mystery wicks" occur to pick off client accounts.
We can see that most crypto market participants can't even distinguish the difference between an exchange vs. Brokerage. The fact that these e-brokerage firms are falsely claiming to be legitimate "exchanges" is a red flag from the get go.
I'm not saying that business model is "bad". It's probably the easiest way to exploit the stupidity of most newbie traders looking for a shortcut to wealth; and personally I think these lazy newbs deserve to lose their money. It's just the shops don't need to lie about it. Why not be honest about their business model like the CFD/Forex shops? You'll still have a shitload of dumb asses willing to throw their money away on over-leveraged bets, all the while develop a better reputation for the industry.