[pw0ncakes]

It's not, at least not completely.

Arbitrage and market-making are legitimate businesses that provide liquidity to markets, making it easier for other traders to get fair trades. (Whenever you trade, the fair value is assumed to be somewhere between the bid and ask, so you're paying about half the spread on every share you trade.)

Of course, many hedge funds out there are scams that exist to take fees while taking ridiculous (and poorly-disclosed) risks with others' money, but not all of them are.