MAYBE becuase ayu is the most important and popular asian singer..and she don't need to share the stage with other low leavel artists and give it a favor to A-NATION with her performance...
to be honest...i think that way...ayu is a real DIVA.. and the A-NATION concerts looks very Improvised with alot of Badly dressed singers. and always the most interesting thing is the ayu performance.
ayu need a stage for her own...AYU POWER!