Also many hourly workers don't get to pick their own hours. I know when I was stocking shelves, I only got to work the hours my manager scheduled me for. If I wanted to work more hours to make more money, I didn't have that option. I've got a friend who is a mechanic as well, and it's the same thing there. He only gets to work extra if they have extra work. If they don't have work for him, he goes home (and clocks out).
I'm salaried, and I had several weeks earlier this year where I struggled to put in more than 5-10 hours a week of actual work because business was slow. I still got paid the same amount, though, and was still "on the clock". So it looks like I have less free time than my hourly friends because I'm still at work while they're at home playing video games.