I feel people still don't understand how much a billion is. One Million dollars would still be life changing for most people here, but consider that 1 million seconds ago was 11 days ago, 1 Billion seconds ago was 31 years ago.
To put it in another perspective, a very bad investment would yield you 0.1% monthly. This means that if a billionaire was to invest money the worst way possible, he would have to spend over 1 Million dollars per month to ever decrease his fortune.
If you had an infinite money machine, that as long as you don't spend more than a million per month it just keeps on growing, would you ever work? Yeah, thought so, billionaires are the same, they might have hobbies, and those hobbies might be something others consider work, but they're not working.
I personally believe that if a person ever gets 1 Billion dollars he should receive a letter congratulating them for winning capitalism, and informing them that any cent above 1 Billion will be taxed at 99.9999% (including investments).