The main usage of Android STBs is media streaming. Since these devices are capable of running android apps like games, they can be also used as a game console. As you may know most of android games need a powerful GPU to execute well, therefore, we need to use expensive SOC that contains the GPU as a building block.
Another approach to accessing high-quality games on the STBs is using cloud games. This approach needs a powerful telecommunication chip which practically is cheaper than GPUs.