Nvidia won because their architecture is better. If you do a significant amount of work that can be CUDA-accelerated, you're kinda wasting your time not owning a CUDA-capable card. It's like being a video editor that software-encodes their projects because they don't want to get an accelerator card. It's your choice, but software-acceleration is a nightmare compared to how quick and efficient hardware-acceleration is. Competitors will all use the accelerator card and ship faster than you can.

Apple, AMD and Intel have all earned their current position by abandoning Khronos and refusing to build their own GPGPU architecture. If the entire industry refuses to invest in complex technology just because it's expensive, then they don't deserve to make money.