have been wondering for a while why HFTs exist when exchanges have holidays and trading hours [1]? doesn't the sub-milisecond speed contradict to the several h

have been wondering for a while why HFTs exist when exchanges have holidays and trading hours [1]? doesn't the sub-milisecond speed contradict to the several hours pause in trading? wouldn't be possible to impose some kind of a delay (say an hour) on all participants? [1] https://www.nyse.com/markets/hours-calendars https://www.nyse.com/markets/hours-calendars