haha. I never really thought about it that way but i think you have a good point but it isn't exactly the same as the MLS / more prestigious soccer leagues out there. In cases such as Rooney, Henri, Beckham, Dempsey it was a question of them getting better pay and probably also much better chances for sponsorship of other sorts.
It is quite rare that we see MLS players move on to other leagues though. Only one person comes to mind immediately and that was Jozy Atidore... but i see now that you don't really like soccer so I might not be speaking your language.