Consider nuclear nonproliferation. It doesn't only affect weapons - it also affects nuclear power generation, nuclear physics research and even medicine. There's various degrees of secrecy to research and technologies that affect "tools that people around the world right now are using towards personal/professional/capitalistic benefit". Why? Because the same knowledge makes military and terrorist applications easier, reducing barrier to entry.
Consider then, biotech, particularly synthetic biology and genetic engineering. All that knowledge is dual-use, and unlike with nuclear weapons, biotech seems to scale down well. As a result, we have both a growing industry and research field, and kids playing with those same techniques at school and at home. Biohackerspaces were already a thing over a decade ago (I would know, I tried to start one in my city circa 2013). There's a reason all those developments have been accompanied by a certain unease and fear. Today, an unlucky biohacker may give themselves diarrhea or cancer, in ten years, they may accidentally end the world. Unlike with nuclear weapons, there's no natural barrier to scaling this capability down to individual level.
And of course, between the diarrhea and the humanity-ending "hold my beer and watch this" gain-of-function research, there's whole range of smaller things like getting a community sick, or destroying a local ecosystem. And I'm only talking about accidents with peaceful/civilian work here, ignoring deliberate weaponization.
To get a taste of what I'm talking about: if you buy into the lab leak hypothesis for COVID-19, then this is what a random fuckup at a random BSL-4 lab looks like, when we are lucky and get off easy. That is why biotech is another item on the x-risks list.
Back to the point: the AI x-risk is fundamentally more similar to biotech x-risk than nuclear x-risk, because the kind of world-ending AI we're worried about could be created and/or released by accident by a single group or individual, could self-replicate on the Internet, and would be unstoppable once released. The threat dynamics are similar to a highly-virulent pathogen, and not to a nuclear exchange between nation states - hence the comparison I've made in the original comment.
I also worry every time I drop a hammer from my waist that it could bounce and kill everyone I love. Really anyone on the planet could drop a hammer which bounces and kills everyone I love. That is why hammers are an 'x-risk'
Which is why you take your course of antibiotics to the end, because superbugs are a thing.