I am not going to argue that some work is more essential than other work, but I disagree that some jobs are created just to keep people busy. Why would anyone hire someone just to make sure they stayed busy? That is simply not happening. The people who control the money aren't worried about keeping people busy, they are worried about making more money.
Now, is there a large part of our economy that only exists because people who have capital will pursue anything in order to grow their capital? Yes, absolutely, but those jobs still exist because someone else will give them money to obtain what the job produces. Companies aren't sitting around thinking, "oh man, too many people in the world aren't busy... let's create some more useless jobs"