Another reason is that XCode and Messages are rapidly-moving targets. Even if you develop something with feature-parity, by the time you get there, the puck wi

Another reason is that XCode and Messages are rapidly-moving targets. Even if you develop something with feature-parity, by the time you get there, the puck will have already moved quite a ways. I felt this is much the same reason why projects like ReactOS and GNUstep, while I consider them great achievements, have not seen mainstream adoption. They achieved great things, but the puck had already moved.