Is the employer obligated to provide social insurance for the worker, even though this insurance is commercial, and what are the repercussions of not providing insurance on the worker's health and financial future after retirement?

Commercial insurance is forbidden, and it is impermissible for a person to subscribe to it voluntarily. Therefore, it is not permissible to compel an employer to provide it. What you anticipate regarding the costs of medical treatment and retirement does not justify committing what is prohibited, for every soul has its provision and its appointed time. One should fear Allah and rely upon Him, taking what He has permitted and abandoning what He has forbidden.