Why Use Futures

More Volume

In December 2022, ETH futures had over $375B trading volume (SOURCE), while crypto trading volume in the same month was $357B (SOURCE). So the contracts for a single coin can have more volume than the entire spot market.

Lower Fees

In most exchanges, Futures have lower fees than spot markets. For Maker Fees:

Binance: 0.1% Spot, 0.02% Futures

Kucoin: 0.1% Spot, 0.02% Futures

OKX: 0.08% Spot, 0.02% Futures

Mid-Market Rates

In Lending Markets, the exchanges will usually take a percentage of the interest rates. For example, Gate.io charges an 18% Service fee, while OKX withholds 15% as an insurance fund. So we can have a lender earning 8.2%, while the borrower pays 10%

Meanwhile, with futures there are no fees on the funding rates. In a similar scenario, the Long contract could be earning 9% and the Short paying 9%.

Leverage

Binance offers up to 125X leverage on futures trading.

Availability

Trading with Futures allows exchanges to offer investments in coins even if they don't offer it on spot trading. Futures can allow shorting in coins that aren't available for margin.

Finally, being a synthetic investment, they can be set to track anything. For example, FTX had the Dragon Perpetual Futures Index, tracking a basket of chinese cryptocurrency investments.