A social contract is an implicit agreement that everyone more or less accepts without anything being necessarily legally binding.
For example, the courtesy of two weeks notice in the US is a social contract: there’s nothing legally requiring it, but there are _social_ consequences (ie: your reference might be less positive) if you don’t follow it.
Everything that’s kind of in an employee’s favor is not socialism. You don’t have to like the idea of “work hard, help the company do well, get rewarded,” but that isn’t socialism. It’s just a thing you don’t like.