A single instance doesn't demonstrate an industry trend. At the time the US made those labor laws what was the trend in the industry?
If anything, this demonstrates the stubbornness of many businesses. Despite seeing ample evidence of success by a peer they tend to ignore it and continue the old ways.
True that a single instance doesn't demonstrate an industry trend, much less a trend in general. However, Henry Ford did have thousands of employees, and does provide some indication to human motivation. However, that was in the early 1900s in the US. Human motivational factors in the early 2000s may be quite that different.
I seem to remember 40 hrs was a compromise - a 4-day work week was proposed, and job-sharing was proposed. President compromised on a federal standard 40-hr work week.
If anything, this demonstrates the stubbornness of many businesses. Despite seeing ample evidence of success by a peer they tend to ignore it and continue the old ways.