If you want the savings, then you need to carry the appropriate card for it, it is not the store's responsibility to keep one on hand to scan for you. If you just can't bear to carry the card then don't expect a discount.

I doubt the employees have any say into when they stock the shelves, they can't just suddenly decide to do it at night and make the putting away of new items the responsibility of a different shift.

If the store bothers you this much perhaps finding a new store to go to would be better.