Because of their reputation as an employer, particularly if they’re hiring employees that have in demand skills. Many companies do have the foresight to want to maintain a reputation of being a good place to work.

I never said they legally have to but they morally should … that’s the point.

Yeah, this sounds like a PR nightmare, they should really give OP decent compensation after convincing him to uproot his life only to pull the plug. If they really left him high and dry I’d be tempted to go nuclear on them, social media, newspapers etc.