Is a GPU doing the same size task as a CPU? If so, why does the GPU need 2GB, 200 times more than the CPU's 10MB?

VRAM is VERY slow compared to CPU caches, which is why GPU apps are designed differently to make the most of the hardware. While it's possible to reduce the memory requirements, doing so would negatively impact performance. Given that all modern GPUs come with more than 2GB of VRAM, optimizing the app simply for minimal VRAM usage isn't practical.