You can also do some simple math to arrive at a justification:

Assume a 4k x 2k display at 60 FPS.

Compute the throughput needed (Bytes per second) to draw an RGB framebuffer.

That is: 8M pixels x 3 Bytes x 60 fps = 1.44 GB/s

Note how we haven't done any computation yet to decide what the colours should be, this is just the CPU effort to do IO to tell the GPU about the new colours to show.

This would incur significant CPU usage, and your device would get hot quickly. In contrast, if you let the GPU scroll, you have to send two floats (for X and Y offset) per frame, and the GPU just does a hardware-parallelised lookup.

This is why we have GPUs, and why scrolling immediate-mode would make your device burning hot while a GPU does the task with minimal energy usage.