Two instances immediately come to my mind when I think of it. Number one is the normal, "nice" rich people that work to keep themselves busy, or because of a passion or something of the like. There are plenty of people(definitely not the majority) that are set for life but who continue to work to better the world, or just due to that particular passion of theirs. Even without that well-meaning or passion, I'd imagine a lot of rich people would probably not know what to do with their lives without work. It's easy for us to imagine how nice it would be but I'm sure a lot of these people need a routine or something to do. Work provides that. Plus, the work most of those people take up is not exactly all that grueling. 

And then you have the greed aspect too. There are a lot of horrible people out there that no matter how much money they've accumulated, or simply were just given, they *need* more. They need a bigger house, a better car, a better life and another golf course or some shit. It's ridiculous. They literally think of people that weren't born with a silver spoon are trash and that the only reason someone can't be like them is because of laziness. So, they gladly take more and more. But hey, whatever floats your boat I guess. 

I didn't mean to get so aggro during that last part. I meant to write simply about greed but I've had a beer or two and thinking about those greedy asswipes got to me. Anyways, YEAH!