How are they a captive??? They agree to the notice period when they sign the contract. A notice period only means that you cannot just up and leave (unless you are fired). When you tell your boss "I quit", you still have to finish your contract. When I quit my job earlier this year, I worked for another two weeks making sure that other people in the company knew what to do.
I'm astounded that the US doesn't have notice periods. They are considered very good business practice over here.
I'm astounded that the US doesn't have notice periods. They are considered very good business practice over here.