>Do you really expect the typical person to set a bunch of passive limit orders on GDAX until they get filled? What kind of user experience is that? I would be willing to wager that 95%+ of Coinbase users are just buying and selling directly on Coinbase (and paying the extremely high fees) and have no idea what GDAX is.

Of course that's the case. I never said everyone does that. I said it's a no-brainer to do it.