While it is a big incentive for sure, I wouldn't be so quick to dismissive it as the main incentive. A lot of the people who are "indentured servants" (as the people here like to say) are not really the kind of people who would "jump ship". In fact, the selection process is already such that only the really pliant ones are sent to the US.

Which makes me doubt whether this step would make any difference to the problem of H1B abuse. However, it would make a HUGE difference for those who are not abusing the system.

Disclosure: I'm on an H1B visa. Of course I want it to be easier to change employer. Who doesn't? Its like a fundamental right.