Why are cashback sites willing to reward me?
Each time you buy a product through a link on a cashback site the cashback site earns a commission from the retailer and basically to encourage you to use their links the cashback sites are willing to share this commission with you so that you continue to shop through them and they continue to earn commission. It is basically a Win Win Win situation as the retailer makes a sale and generates a profit, the cashback site earns a commission and make a profit and you get the product you want and earn a reward for buying something you were going to buy anyway.