There are few reasons why the world is concerned to hear that Queen Elizabeth II won’t be at the Commonwealth Day Service. The first is that it is an extremely important event for the royal family. As mentioned above, Queen Elizabeth is the head of the Commonwealth and normally gives a reading at the service. According Royal Central, that job will now go to Prince Charles, who is next in the line and will someday be doing it anyway.
The last time that Queen Elizabeth was not present at the Commonwealth Day Service, with the exception of last year’s COVID cancellation, was in 2013 when she was sick (via The Guardian). While the Palace did not name illness as the reason that the Queen will not attend this year, she did just recently test positive for COVID-19 in February. She was put on “light duties” during her recovery. The Commonwealth Day Service was set to be her first in-person engagement since 2021 (via Royal Central).