It’s much much more complicated than that. They do typically use CPUs but there are many reasons for it. Starting with the fact that the path tracing algorithm

It’s much much more complicated than that. They do typically use CPUs but there are many reasons for it. Starting with the fact that the path tracing algorithm is quite different when it runs on a CPU than on a GPU because thread divergence is a fundamental aspect of that formula. Second, the vast memory requirements are much easier to handle on a CPU than a GPU. There’s also the decades of man hours spent on the CPU code that is not so instantly ported to GPUs. Honestly this list goes on and on.