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.
Developing technology is a never ending idea as what we people have been doing. With the birth of the cryptocurrencies, it's likely that it opens a lot of possibilities like with this kind of platform. So, we should expect that this is going to be more useful in the future.