Why is a social media site advertising on bus shelters?

Facebook advertisement, transit shelter, Vancouver, BC

I don't get this? Transit advertising works if you are trying to raise awareness. It works well if you are targeting a young audience that takes the bus. 

In a city like Vancouver what young person, or pretty much any nerson, is unaware of Facebook? I fail to see what this campaign is trying to achieve. Almost 1.4 billion people around the world use Facebook. And for those not using it will an advertisement on a bus shelter convince them to sign up?