At most workplaces, the 8 hours only includes time you actually spent working, excluding lunch breaks and commute time. Add that to the time you spend preparing for work (dressing up, doing make up, showering, etc.) and it's more like 10-11 hours total. And some people have the motivation to answer work emails/phone calls outside of office hours!
Add in 6-8 hours of sleep, breakfast/dinner, dishes/chores, etc. and you have might have 1-2 hours left for "recreational" activities such as TV, bedtime stories, other hobbies, sexual intercourse, etc.
No wonder there are so many stress-related physical and mental health problems in the U.S.! The ideal workweek for a healthy work-life balance is 25-30 hours/week.
(I'm not including professions like "Wall Street financer" or "startup company founder" or "health care professional," where workers voluntarily trade long hours for potentially lucrative salaries. The standard workday is 8 hours/day for even the least glamorous of occupations, and that's simply unacceptable.)