Seems that today's Samba Stars are Megastars, and end up spending more time doing adverts etc than they do training. Look at the afore-mentioned Roberto Carlos, Robinho, Rivaldo, Adriano. They were at one point the best players in their position on the planet. The fame that came with that has affected them adversely, and they have all had to return to Brazil to get away from the glare of the cameras to rebuild themselves as footballers and people.
I agree with that for all but Roberto Carlos. I think his was more to do with his age. He was easily the best left back in the world for a long time, then he left Real Madrid and went to Turkey and maintained a good level of performance before going back home.
However, Rivaldo & co. definitely let the fame get to their heads. Maybe to do with the less privileged backgrounds that they had as youngsters and it leads to them milking it?