There was a time when nuclear disarmament was actually happening. That is passed now, of course.

Incentives were aligned better there, though. Disarmament happened only to the extent it didn't threaten the MAD doctrine, and it reduced ongoing maintenance costs for everyone involved.

> Disarmament happened only to the extent it didn't threaten the MAD doctrine, and it reduced ongoing maintenance costs for everyone involved.

The U.S. and USSR were the only countries embracing MAD. The other nuclear powers embraced flavors of what we now call minimal deterrence [1]. (Think it's helpful to know deterrence theory has options other than MAD.)

[1] https://en.wikipedia.org/wiki/Minimal_deterrence

Few countries have obtained nukes only to later relinquish them.

South Africa did, because the outgoing government didn't want to hand nukes to its successor government.

Ukraine, well, see how that worked out.

Kazakhstan, Belarus... seems ok for them so far.

On the other hand, those who have weapons tend to want to keep them out of the hands of whoever their subjugating or oppressing. See the history of domestic arms control in damn near any country for examples.

Yes, same with ABC-Weapons. Why would anyone with the technology ever want to disadvantage themselves?

Because of the inevitable destruction of the human race from an ever escalating set of wars.