RX1: stupid question about aperture ring

I'm not used to having the aperture adjustment on the lens barrel itself, but I'm sure there are good design reasons for having it there. Would just like to know what they are. Perhaps I'm not holding the camera right, but I'm finding it 'inconvenient' to be turning the aperture ring when setting up a shot. Would be great if either of the wheels/dials on the back of the camera could be used for controlling aperture, but it seems they can't. In fact, seems like they do absolutely nothing in A-priority. Or am I missing something?