Be fair kenjit, ATC started introducing curved slightly tapered side panels to their domestic cabinets a few years back. You can be sure they did it for good sonic reasons.
It looks like ALL their professional speakers are boxes. We all know boxes are bad.
Having curves doesn't stop it being a box. Its still a box. You gain nothing from having slightly tapered side panels. Its just cosmetic. Hence they do it on their hifi speakers because appearance is important to audiophiles.