The truth is a bit more nuanced than that. Henry Ford did not institute a 40-hour workweek out of the goodness of his heart. In an interview to World's Work magazine in 1926, he said: "Leisure is an indispensable ingredient in a growing consumer market because working people need to have enough free time to find uses for consumer products, including automobiles."
In other words, he understood that a consumer-based economy needs consumers, and consumers need sufficient leisure time to be able to go shopping and buy things.
Louis Brandeis had similar beliefs. Leisure was important for workers and his battles against the monopolies of the day were often focused on this belief. Though his focus was on self-growth and learning in the leisure time provided.
Your understanding of this subject disagrees with history. Henry Ford did not create a 5-day work week. Unions had already been fighting for an 8-hour workday for 60 years in the US alone. Ford adopted this and a 6-day week to attract workers. One could almost be forgiven for concluding that Ford was won over by 60 years of arguments and political activity by unions that preceded him, and gave their ideas a try.
Henry Ford did not bring American workers a 5-day work week. Unions had been working for the 8-hour day for more than 60 years before Ford tried an 8-hour, 6-day work week to attract workers who were already demanding an 8-hour workday.
> For instance, Ford’s " ‘sociological department’ had to inspect a worker’s home to make sure they ‘deserved’ the $5 first," said Ileen A. DeVault, a professor of labor relations, law and history at Cornell University.
In other words, he understood that a consumer-based economy needs consumers, and consumers need sufficient leisure time to be able to go shopping and buy things.