His main reason is for money, though no doubt he enjoys playing.
David Beck-ham makes 57 million (AUS dollars) dollars a year is the worlds highest paid soccer player.
Tiger Woods (golf) and Alex Rodriguez (baseball)
To be honest i like leonel messi better. But Cristiano ronaldo makes more money by the fact that he makes so many commercials and advertises many brands.
Alex Rodriguez has the highest salary on the Yankees. He makes $33 million a year.
Alex Rodriguez makes roughly 25k per year
P. Rod makes about 6 figures in a good year.
For the 2009 season Alex Rodriguez made the highest salary at $33,000,000.
David letterman makes 40 million a year