Nuclear weapons shift from a very high probability of something with relatively small consequences (conventional war) to a low probability of something with absolutely catastrophic consequences.

What risk of global catastrophe is worth it to reduce or end conventional war? One in a million per year? One in a thousand per year?

The actual risk of nuclear war is extremely hard to estimate. My reading of Cold War history is that it’s closer to one in a hundred per year than one in a million. Having a multitude of nuclear-armed states makes it worse. I don’t find this tradeoff to be even remotely worthwhile.