There's a lot of Avex artists that don't perform at a-nation. Hitomi doesn't perform, V6 doesn't perform, DA PUMP, Shimatani Hitomi, speed (they're back together now), Jeanne de arc...

Chances are Namie probably was working on a new album. She hasn't had one in a long time (if you don't count the Suite Chic album). Other than that, she's only had a few singles. Nothing really new to go on tour for. All the other artists on there have had several singles or an album come out within the year.

At least that's my take on it.