Big (and little) stars have always done adverts for the reason given by VHG. In the good old days they japandered themselves (Japander: n.,& v.t. a western star who uses his or her fame to make large sums of money in a short time by advertising products in Japan that they would probably never use) - decades of such behaviour has obviously removed any remnants of shame in being seen in Western adverts.
That's spooky - I was just sat thinking that to myself when this thread popped up in latest posts. I had taped the Phil Spector biopic with Al Pacino on the off chance that it might be good and that set me thinking - why would he star in something like that and why the adverts? It just felt as if you were reading my mind - Have I been bugged?? do I need to update my firewall?