Why are people taking pictures of the tea ad at Shibuya station?

There's an ad for pretty normal-looking bottled black tea just outside the Hachiko gate. Almost every day since it's been there, when I pass on my commute, there's been someone (always a woman) taking a photo of it. There's no QR code or anything.

This is driving me nuts. Google is no help at all. Is there a contest or something? Why take a photo of this specific ad? I never saw anyone doing it with the last ad in that space.

by emote_control