Since Prince William and Duchess Kate Middleton can’t celebrate the holiday publicly, the typically fill their schedules with other things. In 2017, the duchess indulged in her favorite sport, tennis. She visited the Tennis Lawn association which teaches young children, ages 5 to 8 years old, how to play and enjoy tennis.
British royal family is known for their charity work. For Halloween 2017, a still single Prince Harry was in Chicago, visiting with former First Lady Michelle Obama for the inaugural summit of the Obama Foundation. Even if the royals wanted to celebrate, their schedules won't allow them to celebrate.
Though it wasn’t for Halloween, in 2005 when he was 20 years old, Prince Harry found himself in quite the pickle when he dressed up as a Nazi officer for a costume party. People were disgusted and horrified by his behavior. The tabloids labeled the prince, Harry the Nazi. He ended up releasing a statement saying he was “very sorry if I caused any offense or embarrassment to anyone.” Now, it's pretty much clear why Halloween is banned in the Royal Family.