[cperciva]

If you have a boring 8 hour day job, you still have sixteen hours left in the day.

Of course, you're going to spend 6-8 hours out of those 16 sleeping. And 1-4 hours travelling to and from work. And 0.5-1 hours preparing and eating breakfast and dinner (I'm assuming you have lunch during your 8 hours at work). And at least 0.5 hours showering/shaving/brushing teeth/getting dressed/etc.

focus hard enough and you can get a decent 6-8 hours for a quality coding spree at minimum

If you only need 6 hours/day of sleep and live five minutes from where you work, sure. But for most people there simply aren't enough hours in the day to stay alive while working two full-time jobs.