They need to take fee so the website can run, cause you know a website like exchanger need to pay a bill for domain for example and his hosting. I rarther pay a fee than trading for free but one month later the exchanger dissappear and all my money gone though
Before I say this, I will be very straight forward that their concept is not EXACTLY all that clear, as it's in early stage. But I have absolute believe that it is POSSIBLE for an exchange without charging fee from trader, BUT a lot of thinking got to be done in that scenario.