Sounds like this is just wishful thinking on your part, then.
If you strictly work 40 hours a week (no OT), have 0 commitments outside of work, don't have a considerable commute (i.e. fewer than 30 minutes total per day), and can easily get by on 6-7 hours of sleep, then yeah--you'll have a good chunk of free time.
But once you subtract time for driving to work and then back home, your lunch break (which, if you take an hour, you're really at work for 9 hours), working out, running errands, cooking, cleaning, SLEEPING, etc., you quickly realize that your free time is more like 4-5 hours a day instead of 8.
And for those few precious hours of free time you DO get, you're too fucking mentally or physically exhausted to do anything other than sit around and mindlessly consume entertainment.