No fees wouldn't guarantee that it would cause a more loyalty to their investors/traders. Remember that the exchange needs a lot of things to operate, include the server, domain name, etc. They could earn those maintenance cost from the fees coming from their users excluding the mining fees.
Lowering to a reasonable amount is still okay, but having no fees is a no-no.
It is true. I do not mind that, if the fee is comparable to the quality offered by the exchange, including the security and speed of the transaction, that makes me comfortable doing the exchange. After all, we give the fee for using the exchange service, nothing is really free right in this world? so this is a symbiosis of mutualism. And the most important thing here is the excellent service provided by the exchange, with a good system support, responsive to any obstacles, that's what I need the most. After all, we can choose the exchange we want, moreover, the fees are dynamic, so we can choose which is the most effective. I still prefer high fees but good service, rather than free fees but it takes hours to complete each transaction.