As Homo sapiens we have been naturally selected as people who can cope with grinding hard work, lack of sleep, the ability to channel adrenaline into survival etc. If we then become rich and have lots of leisure time it can affect our happiness level because we are the survivors, the ones who struggled to be here, the ones who made it. As a species we're not biologically cut out for sitting around a pool all day.
I think this is what Getty and other rich people mean, but then there's plenty to be done if you are awash with cash. Plenty of need in this world if they get bored by that pool.