The shop is doing itself a disservice by having a schedule for attaching the discount stirckers. Why? Needing to use those stickers, or rather needing to systematically discount merchandise, is just a side effect of how impossible it's to know for sure how much stuff you need to have on the shelves. Obviously a shop would want to sell everything at the normal price, with a good profit margin. But it's also not good to lose sales by not having enough for all customers. Having empty shelves is also bad for the image, leaving potential customers dissatisfied and not coming back. So, typically a shop ends up having too much and then getting rid of the excess by discounting them. At least you can cover your own costs even if the profit is far less.
This is not supposed to be any extra service for customers hoping to save money. It's merely a side effect of the business model. Thus making it more like a part of the normal business by having a schedule doesn't serve the business. It only encourages the type of customers who expect to get discounted stuff automatically, either because they misunderstand what it's all about or because they are feeling entitled.