[goostavos]

I think it's more that they're fairly indentured. Their visa is tied to a specific _kind_ of work, they're legally prevented from making money in any other way other than their current job, and while they can change jobs, my understanding is it is generally viewed as risky (for instance, if the new place doesn't work out, you've got a few short months to find employment or your visa is no good and you have to uproot your life)

It'd be really interesting to see data on how often H1B's change jobs compared to the rest of the population.