Another point is that even if the GPU would do very little computing, you would need something able to communicate between your screen and your computer. This is similar to external sound cards and network cards, although these are not so common these days because for most users the integrated cards are fine.
fluorihammastahna t1_j6mgwod wrote
Reply to ELI5: Why do computers need GPUs (integrated or external)? What information is the CPU sending to the GPU that it can't just send to a display? by WeirdGamerAidan
Another point is that even if the GPU would do very little computing, you would need something able to communicate between your screen and your computer. This is similar to external sound cards and network cards, although these are not so common these days because for most users the integrated cards are fine.