We don’t get employment contracts anymore, ever since every state passed “at will” employment laws. Companies can drop you at any time for any reason that isn’t one of a very small list ( racial discrimination, union retaliation, etc) with no notice to you beforehand. They also don’t need to provide any real proof for their reasons unless you file a lawsuit, there are plenty of stories of companies getting wind of possible unionism and they fire groups of people for being late occasionally or the location was underperforming when really it wasn’t.