Very useful for Machine Learning stuff. And for Crypto though that has fallen out of fashion nowadays.
Basically if you're doing a fuck-ton of math and want it to happen very fast, you want to use a GPU to do it (GPUs are literally made for that -- That this helps them draw video games is a happy consequence), and NVidia's CUDA tech makes it... Easier? Faster? Not sure what the proper difference is, but yeah.