I wouldn't say that I live to work, and I definitely need my breaks, but I haven't been without a job for more than 2 months since I was 15. If I made a windfall, I couldn't quit my job and travel the world for a decade, I'd go crazy. On the other hand, I have some friends who simply don't like working. They can't hold down a job for more than 6 months, and just bounce around doing whatever odd jobs they find.
The challenge comes when we put our energy into work in places where our output is squandered. For a great example, imagine the game developers who built entire AAA games, only to see their games canceled just before release. Yes there may be many reasons for the cancellation, but the feeling of wasted time and creativity is real.
Manual labor is practical, and it can be useful and even meditative. Unfortunately, it usually doesn't pay enough to live in most modern areas of the world.
I don't know the age of your friends, but I would posit that they bounce around because they have a strong sense of "this is not right" when they get into a job. I have had more satisfaction from some of my days waiting tables (providing a really good dining experience!) when I was young, and I have had some soul-crushing days sitting in futile meetings about projects that were doomed from the start at big companies. If you asked me during those meetings, I would have rather been a waiter making $3/hr + tips. At least then I would be making people happy.