Many industry leading websites have the similar feature/promotions where you have to complete some missions (play x amount of hands, get x pair, etc.) in order to unlock some reward. Usually these rewards are close to nothing (few cents).
@TonPoker can you post your detailed rake structure here across all formats? It would be helpful if you can post all leader boards + cashback rearwards also, I just want to check if if is possible to beat the rake in your platform.