Possibly due to aircraft and staff constrains? Guess they wouldn’t want the mass cancellation to happen again like earlier this year.

But I agree as an airline, having schedule fixed in advance is important in getting planes filled. Now that we always see skyrocketed prices when book in further advance, and deep discount for last minute tickets. Let alone the PEY issue on short haul as mentioned above. This is obviously not a sensible way to fill planes, and potentially damaging the reputation.