It is really, really hard to apply for an H1B for a candidate unless they just graduated from college and are on OPT. If they are on OPT they basically have 2 chances to apply for an H1B. If you don't, then the employer would have to apply on your behalf on April 1, with a coin-flip probability of getting one, and even if they got one the employee couldn't start work until October 1. That makes anything except an H1B transfer prohibitively risky and inconvenient.