Maybe this question doesn't properly apply to USA programmers since labor laws are a little different there, but let me try.
Rationale: we always discuss how programming makes us tired and stressed, how often we spend hours and hours per day just procrastinating or being completely unproductive while still trying to be. Also, we often discuss how programmers get paid nice salaries in comparison with most other professions. This leads me to the conclusion: I'd probably be very happy to take a 25% (or more) salary cut if I had to work 25% (or more) less. I mean, 8 hours per day is a lot and it's very rare for me to have a fully productive day. If I moved to 6 hours per day, I'm not even sure if I'd become less productive, I'd probably just spend less time chatting at the coffee room, and have a smaller chance to get burnout. Maybe a little less productive, but the company would be saving some money with me, and if they did this to other 3 people they would be able to hire another 6h/day programmer to balance things, maybe making the result even positive for them.
But, considering that no company does this, it looks like this isn't a good idea for employers. Why? Why do companies try to squeeze all the possible juice from employees instead of the alternative where they pay a little less, require a little less, and the employee becomes much more happy?
And the question to the workers: wouldn't you accept a proportional salary reduction for a proportional time-spent-inside-the-office-doing-whatever reduction?