And if you have kids, it's even harder because if you're planning to leave them an inheritance you'll leave them more if you keep working. The same applies for high earners who are committed to philanthropy: the longer you work, the more you can donate to the causes you support. Once you retire, your level of giving typically declines.
That's exactly the point. If you're pulling in $750-$1 million/year, it seems like a tragic waste for you to give up something that allows you to do so much good even if you're a do-gooder and not a big spender. Think of it, you could retire and give 20 hours a week or so to your favorite charity or you could keep working and give them $250,000/year and transform their whole mission.
Frankly, I don't make quite that much yet, but I sometimes find it crushing to think about the value of my time. It is really hard to relax when you know every hour of your time is worth $600+.