Yes, what` s that all about? why don`t they just reduce the price in the first place, or are they relying on people forgetting to claim it?
Who are "they" in this context?
Manufacturers could reduce the price they charge to retailers, but that's undesirable for all sorts of reasons.
For starters, retailers will already have stock for which they paid full price, so they'll want to clear that before dropping their prices. And in fact there's no direct compulsion for them to reduce their prices at all - the manufacturers can't insist on this. So the manufacturer's price cuts will feed through into retail price cuts slowly and unevenly, if at all. Additionally, any retailers that have (deliberately or accidentally) turned their stock over faster will be able to offer the discounts sooner. That would put other retailers, who (accidentally or deliberately) have larger stocks, at a disadvantage. It might also lead to claims of favouritism. Best avoided.
And at the other end of the promotion, retailers might choose to stock up on items which they're buying for a reduced price, so they can afford to continue the promotion for longer. Again, that puts other retailers at a disadvantage, especially if they've wanted to stock up but haven't been able to, and again it risks claims of favouritism.
By offering the price cut directly to consumers, the manufacturers have much greater control over when it takes effect.