These rich bitcoin holders are probably just holding their coins hoping to be richer in the future when the price increases. To say the truth 1 million of dollars is nothing nowadays to have a real rich life.
To live well they need to continue holding until bitcoin increases more its price and making investments meanwhile.
Yes some are still holding it because they believe that its price will increase in the near future. In the other hand, I salute for those people who doesn't forget to thank btc for bringing them to be a rich one. They are still humble and thankful for all the bitcoin did in their life to be in their position right now. And I hope that bitcoin will help more people to become rich someday.