The main reason is basically that the Wii uses unified memory, so the CPU can change things that would normally be in VRAM on a PC. This means that things often need to be streamed to the GPU as and when needed in case they've been changed.
OS: Windows 10 64 bit Professional
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
