Yes but as well known public figures they automatically are assured of an audience. That is what is needed for the message to reach the most people? We don't know how they help in their private life, but I wouldn't assume they donate nothing.

Bono's giving is legendary and Kate Moss and Kylie both are helping raise huge sums with their breast cancer awareness work. They all feature in the ad you speak of,it isn't their fault they are well known people, at least they all offered to be in the advert and get it plenty of air time in the process.

We can have faceless doctors lecturing us every night on the news, telling us what the problems these people are facing through poverty, but it doesn't get the media attention needed to make the difference unfortunately.