Why is cash back a reason to buy a product?

I have seen a lot of tech adverts not from retailers, but from manufacturers (mainly camera manufacturers) E. G. Cannon, Nikon etc advertising cashback as a reason to buy their product. (e.g. £35). How is that appealing? Surely when you buy any product from a shop you can get cashback anyway?

But you don't… Why would a retailer give cashback? They'd just discount the price.

Well a fisherman puts a big fat worm on his hook doesn't he and the ones who's eyes are bigger than
their bellies bite

Its not a good reason to buy a product. Its just a discount but its a discount you probably have to do some work to get.

The fact is that you usually have to apply for your cash back between specific dates and it is a hassel to claim back eg write a letter of submit a form. Most people don't apply in the right way or at the right time and so often less than 10% of people get the cash back from the companies.

They offer it as insentive knowing they will only pay it to a small proportion of people.