That's probably part of it, but also the "mutually assured destruction" is saving us from the mutually assured destruction. No one wants that horror in their own country, and no one believes their defenses are good enough to prevent it if missiles start flying.

This is probably realistic. Modern ICBM designs carry multiple independently targeting warheads, plus decoy warheads, but can't travel fast enough to reach a rival nation before they can launch their own missiles. If launched, every nation with such weapons has the capacity to completely overwhelm any anti-missile defenses, but not to prevent retaliation.

This situation becomes unbalanced when:

1. Someone develops a practical method for shooting down 10 actual warheads per missile while correctly identifying the decoys and either avoiding or shooting them down too.
2. Someone develops a faster delivery system and/or a reliable way to blind early warning systems (unlikely because you would need to blind multiple space and ground observation platforms at the same time).
3. Someone rises to power who doesn't care about the consequences to their own nation.

Personally I think the fear of dying horribly is still the largest factor. The US has probably invested the most in developing a practical ICBM interception system:

https://www.mda.mil/system/system.html

...and that pretty much just gets you to "we can probably prevent half the warheads from reaching their targets".

Also the point where, if one starts throwing them, likely others will follow and that will basically kill us all

Which is why I'm so fucking terrified of the religious death cult guys in charge of the US government

Say what you want about the USSR (it was a shit place), but at least they had some cool heads there that on more than one occasion avoided WWIII

Actually Second Strike capability is the great deterrence.

If an aggressor can't knock out essentially all of their enemies nuclear response capability on the first strike, the return volley will be devastating.

It's why the US developed nuclear missile subs - to have second strike capability.

Everyone seems to forget for about 4 years the US was the only country with demonstrated atomic bomb capability.

They could have threatened any other country to give them the keys to the kingdom as no one else had first strike, let alone second strike capability.

Having your country nuked back will also make a lot of your assets less valuable - and it's also likely that your country is dependent on some big actor who's really invested in the nuclear taboo.

Like, one of the many reasons Russia won't use nukes in Ukraine, is probably because it would seriously piss off India and China, who both have a troubled relationship with a nuclear-armed neighbor.

The fact that mutual dependence contributes to stability and peace is something we don't talk so much about these days... I hope the lesson that reminds us won't be too brutal :\

Modern war with guns and tanks has shown to be very difficult to "win" and still be in power. Vietnam war. Middle east wars. The multiple coups. Usually within 10-30 years, something else happens.

The winner always seems to be the ones who profit the most and are able to plant themselves inside the country and get rich from it.

This is semi-related so spoilers for the Fallout show: this right here is the reason I stopped being invested in the plot of Fallout. When they revealed that Vault Tec dropped the bombs that created the post apocalyptic setting I was dumbfounded. I can accept silliness and characters being nonsensical sometimes, but in that moment every person in that room was proven to be outright stupid. They tried to say that it would let them “corner the market” in the aftermath, but how could they not see that they were destroying their own marketshare too?

the perfect WMD is one that kills the population but leaves all the infrastructure untouched. luckily nothing like that exists, yet

No one is building vacation resorts in Chernobyl.

rebuilding after war is insanely profitable though

But I'd there is radioactive wastes, all the other resources become more valuable because there are around. Using supply and demand as a basic bad model, lower supply means they can charge more for the demand.

I'd think it's because most people don't have nukes.

Yeah du duoy.

Ironically, that's why they invented the neutron bomb: kills everything in its radius, but leaves no radiation behind.