There is no lock. Once you have an H-1B, you can transfer as soon as you get another offer. The lock is on the J-1 and O-1 visas very popular at research orgs. That's where the true indentured servitude happens.
J-1 and O-1 have more shackles. H1b indeed restricts mobility.
IMO, a better law would be to give a green card with 3 yr validity to those on H1b. Then you'll see how the equation changes. Employees on H1b have very few choices due to these locks.
IMO, a better law would be to give a green card with 3 yr validity to those on H1b. Then you'll see how the equation changes. Employees on H1b have very few choices due to these locks.