Most applications expect higher volumes during the day and lower volumes over night. Being able to set rate limits for specific times of day will avoid false positives that occur when you try to set a limit that works for the whole day and will allow for naughty traffic to be blocked more effectively during low load times of day. Without this ability, we're left with setting limits that allow for day time legit traffic volumes which makes it easy for threat actors to fit their attack traffic just under the limit.