Free open markets, anyone?
Multiple exchanges ensure that the markets are not controlled by any one exchange, which can use its monopolistic advantage to increase costs by levying high fees etc.
Furthermore, if one exchange does something shady like front-running, or preferential information sharing with its "partners", then people can just move to another exchange. Basically, multiple exchanges make the markets more honest.
Free open markets, anyone? Multiple exchanges ensure that the markets are not controlled by any one exchange, which can use its monopolistic advantage to increase costs by levying high fees etc.
Furthermore, if one exchange does something shady like front-running, or preferential information sharing with its "partners", then people can just move to another exchange. Basically, multiple exchanges make the markets more honest.