Vulkan is a pain for different reasons. Easier to install sure, but you need a few hundred lines of code to set up shader compilation and resources, and you’ll need extensions to deal with GPU addresses like you can with CUDA.

On Windows: download a 3GB exe and install

On Linux: add repository and install cuda-toolkit

Does that take a few hours?

Haha. People have already said what is Vulkan in practice - it's very convoluted low-level API, in which you have to write pretty complicated 200+LoC just to have simplest stuff running. Also doing compute on NVIDIA in Vulkan is fun if you believe the specs word for word. If you don't, you switch a purely compute pipeline into a graphical mode with a window and a swapchain, and instantly get roughly +20% of performance out of that. I don't know if this was a bug or an intended behavior (to protect CUDA), but this how it was a couple years ago.