With a traditional crypto exchange, you only need to worry about them getting hacked making them unable able to cover their deposits. With a gateway, you have to worry about them getting hacked, and when they issue you an IOU on the blockchain for your deposits, you have to worry about getting hacked yourself and losing that as well.
Assuming that an exchange is secure, its trading website would be much easier to use and more secure than downloading specialist wallet software to trade yourself on a blockchain. The only advantage gateways have is that you can quickly trade the IOUs for market pegged assets to free yourself of counterparty risk, but first weve got an uphill battle to convince people that works.
Will gateways actually become popular and be a preferred option?