Multiple things can happen (or a combination of them). It’s perfectly possible for all the 7 days after the booking window to be fully booked. If there are 10 rooms, and 10 people this morning booked a full week, the room will be unavailable for the next 7 days.
In a regular booking schedule this is unlikely to happen, as most people will have different lengths of stay and check out day, but the day most likely to be affected is the one that it’s becoming available to book the next day.
There’s also things like maintenance, a 2BR lockoff reducing 1BR/studio availability, etc.
People will also say walking. This doesn’t directly causes this problem, but it makes it more noticeable. These days people are walking rooms/dates that are not even necessary year round. You sometimes see this happening for rooms that are wide open, and each day the unavailable day keeps moving.
I also suspect there’s an IT glitch happening blocking days for some reason. I’ve noticed it sometimes when it doesn’t make sense (like the 5th being available and the 6th not).
