Why don’t we have Wayland yet?

The graphics chip (GPU) is called VideoCore and contains hardware for rendering OpenGL graphics, as well as encoding and decoding video streams, scaling images quickly, and talking to HDMI screens (it was originally a chip to go in TV set-top boxes)

When the Raspberry Pi first shipped it came with an old closed source firmware blog to access the VC4 chip within the Pi. Finally, while the Pi has a surprisingly powerful GPU for how cheap and old it is, but it’s still pretty out of date and the lack of source to the graphics driver means no one (other than Broadcom engineers) can fix bugs in it, improve performance, or add features. A modern graphics stack needs the kernel to have real drivers for the GPU, provide controlled access to GPU resources like texture memory, and provide an standard API for applications to code against.

Source: joshondesign.com