Why don't we have GPUs that are swapable just like CPUs are?
We do....
Unless i've totally misread this post?
i don't think they even make on-motherboard graphics anymore, or have for a number of years
If you mean, having a gpu socket on a motherboard, rather than pci-e 2.0 or 3.0, I guess it's better for thermal performance if it's on a seperate pcb with a large cooler. But having swapable gpu sockets on laptops would be amazing.
We already have that for laptops, there are a bunch of Nvidia GPUs for laptops that connect via Mobile PCI Express Module (MXM Graphics Modules)
That'd be nice but everyone's forgetting the reason a graphics card has its own PCB anyway. You don't just have the actual GPU on the PCB. You also have the memory, power delivery, I/O, and all the other components on the card itself. Making a socketed GPU would be like adding a CPU socket, adding another 4 DIMM slots, adding a second VRM, etc.
Also, compatibility would be a nightmare. Think about it -- your motherboard would have to have all the stuff that was on the card soddered onto the board. When you swapped out your GPU you're limited as to its performance. For example, assume you have a board with a socketed GPU, 8 power phases, etc., with 6GB of GDDDR5. Now, 3 years later, GDDR6 is mainstream. You just bought yourself the top-of-the-line GTX 1280, but it only supports GDDR6. See what I mean?