I can't speak for this case, but the answer is often "you found out after you travelled across the country and turned down other job offers, and may be waiting

I can't speak for this case, but the answer is often "you found out after you travelled across the country and turned down other job offers, and may be waiting for repayment of moving expenses". Yes, a person could try to get this sort of thing in writing and sue for damages incurred, but they'd still be unemployed and loaded with expenses in the meantime. There's a lot of freedom to push this kind of thing because there's too much legal overhead to fight it.