It's not.
The ad agency who did the "Eyebrows" spot also did the drumming Gorilla and the airport trucks ads for Cadbury. The ads are meant to be silly, strange, comical . . .
and memorable.
They said in an interview they hoped it would be interactive in a way that people were doing the eyebrow dance/gestures. In the end it doesn't have to pitch the product per se - it just has to catch your attention. Which is obviously did - so they've done their job well.
Here is the link from the Guardian -
http://www.guardian.co.uk/media/2009/jan/23/cadburys-ad-eyebrow
"Like the other productions 'Eyebrows' is all about losing yourself and embracing that moment of joy ... after all, everybody remembers pulling a silly face or getting up to no good as a child when backs were turned."