Orville,
It does seem there's a lot of opportunities overseas when you see all the foreign jobs that employment brokers advertise. Complex equipment, apparently decent pay, varying schedules. I think what you are asking is why are'nt these jobs snatched up quickly by pilots who meet the requirements?
I have to guess that's because going overseas is a big jump- especially for a lot of aircrew who have reached the point in their lives when they are qualified to fly that equipment. Many if not most will have families they want to be with and big responsibilities outside the airplane. I have a friend who works in a pretty crummy place- for great pay, but in order to do that he trades away roughly 2/3 of a year of relative freedom in the U.S., near family and friends, to be over there doing his job. Can be a tough trade when the romance of being overseas wears off.