Do airports need to advertise to the general public?

I was taking a ride on the London underground (aka "the Tube") the other day and an advertisement on the top of the wagon, just above my head, caught my eye...It was a London Heathrow airport ad (see picture) highlighting the airport's role in the UK economy by connecting the country to the World's fastest growing economies...all fine, no doubt about it, but...does the average commuter really care? will you choose to fly from LHR next time because of this? ok, I know, it's a public relations stunt...but, again:

if you are an airport, is an ad on the tube the best way to deliver the message?