It became a standard in the US, but is not a right. And while the idea of the 40-hour work week did, indeed, come from labour groups, it was the Great Depression needing effort to try and compel businesses to hire more workers, not the fight of workers, that pushed to see it become a standard.
A wage is debt, so not beneficial in and of itself. It can be beneficial when you call the debt and turn it into something tangible (e.g. food), of course, but that is also of benefit to the business who derives joy in giving you that food. It is not for the benefit of workers. It is for the benefit of everyone.
It became a standard in the US, but is not a right. And while the idea of the 40-hour work week did, indeed, come from labour groups, it was the Great Depression needing effort to try and compel businesses to hire more workers, not the fight of workers, that pushed to see it become a standard.