Of course, such platforms are used by many people, the most important thing is to find a good platform with favorable conditions.
Similar services are very popular. I know a lot of loyalty systems on the blockchain that are going to release their systems in 2019-2020. But I havent met any projects with cashback system yet.
In the cryptocurrency world, this is a rare phenomenon, and in a normal life a lot of banks provide such a service, you buy and some of the money goes back to the card