25 hours is a good number for average people. I'd say 15-20, even. Ambitious or highly dedicated people will always work more than that, and that's a good thing. What they should have is a lot more freedom in how they spend that time-- working two jobs, one job and school, side projects. The problem is this bullshit conformist fiction in which everyone has to pretend to be ambitious (but only internally) and dedicate…
Today working around 40 hours a week is an important prerequisite for a great many important things such as the traditional suite of full-time employee benefits (health insurance, for example).
Additionally, social security and medicare taxes take 14% of income right off the top, and then federal and state income tax adds onto that. Such high tax burdens make it much more difficult for people to build up their own savings, and it's no surprise that savings rates have plummeted over the years. Lack of savings results in greater dependence on employers and less negotiating capability for non-traditional work hours.