There are different reasons why fighters fight abroad, Ricky Hatton had conquered the UK and became the legitimate world champion here. However in order to break into the US market he has to fight over there. To maximise his money.

Joe wanted to fight in MSG which is a dream come true for most fighters or Las Vegas.

Ward can dictate where he fights, so he will choose where he is comfortable, the same with Floyd because it allows him to use injections in his hands.

The Klitscko are earning sufficient money and have more than enough popularity to not worry about breaking the US market.

Steve Cunningham basically had to fight in Europe to earn a living as he was not appreciated in the US.