Generally a queen will lay in two boxes, unless forced to stay in one box by using a queen excluder. So even if you only use one deep, then other sizes, the queen will still want to lay more in the other boxes.
If you keep her to one brood box, your hive won't grow as big. And sure, that's not a real problem to have only one brood box to go through winter if you live in a nice climate. But there are also less bees to collect honey for you. More bees means more work gets done.