david beckham in USA? for sport or commercial purpose ?

It was a wise move for him. He probably knew that he will be getting more and more rivals in the European football scene that's why he signed a contract with a US team. There are younger and really good players coming out and spectators don't usually go for the looks, they want skills. Al least he can end his European carrer gracefully.

The primary reason may be sports, but definitely theres a a lot commercial appeal and money involved which probably clinched the deal!

I think a lot of the reason has to do with his wife, Victoria. She was feeling quite isolated in Spain and never really adapted to the culture. I am sure they will both fit in very well with the weather, culture and MONEY. The commercial benefits will be for him and of course LA Galaxy, I´m sure they are aware of how much revenue he generated for Real Madrid in off-pitch merchandise sales, and they will be hoping to apply the same formula at home.