It's too much work bro! I don't see people who are really busy using it quite frankly, but I could be totally wrong.
Looking at it from a customer point-of-view, I would be so damn confused initially, not to mention worried about giving my money to a rather new service, that I would rather pay more money with WU or MG than have to deal with that. I want the process to run as smoothly/quickly as possible, and if I'm sitting there trying to figure out EvoCash, when I instead could be off wiring the money WU or MG, then I wouldn't bother with the guy who used it as a form of payment.
From a source point-of-view, I wouldn't bother with it either. AGAIN, you want things to transfer as quickly & efficient as possible. Having to explain how to use EvoCash to every other guy who wants to order, doesn't exactly make for a simple process. The customers you would lose because they are too overwhelmed by it would probably make most switch back to their old payment form.
I could be way off, but after looking at it myself, that is the initial impression I got.