There are cases where you want tons of random numbers (e.g. monte carlo) and the line between "good enough" and "disastrously bad" is often unclear. Providing cryptographic random numbers is the only possible API that's both safe and generic.
As the post says, it's worth entertaining the idea of having the kernel provide a blessed way for userspace to do that, though I admit I've never personally seen a scenario where RNG was truly the bottleneck. But it'd still be nice to kill all the custom RNGs out there.
Don't you always want a reproducible random sequence for such simulations? I.e you use getrandom for the initial seed only, record it, and do the rest of your RNG state in userspace code?
It's a nice property, but a lot of people skip it because of the tradeoffs. I'm also sure there are lots of use cases I'm not aware of where you don't want reproducibility.
As the post says, it's worth entertaining the idea of having the kernel provide a blessed way for userspace to do that, though I admit I've never personally seen a scenario where RNG was truly the bottleneck. But it'd still be nice to kill all the custom RNGs out there.