Acquiring nukes seems like the best way for any country to protect themselves against outside interference.
We know that as soon as Gaddafi decommissioned his nukes, Libya was targeted and invaded. If Iraq actually did have nukes, the USA wouldn't have been so brazen to invade.
China, Russia, and North Korea's acquisitions of nukes are also some of the main reasons why they are not easy targets for direct US invasion.
If Iran had nukes, it would drastically limit Israel's ability to indiscriminately attack Iranian assets.
Western policies against nuclear proliferation always seem to target the countries that need them the most to ensure national sovereignty, and never refer to their own nukes.
For example, they always fearmonger about "rogue states" like North Korea getting nukes, while being perfectly okay with Israel's own nukes. It might be best if these policies are ignored entirely.
I don't think nuclear weapons are the only reason, just a primary one.
The U.S. would sacrifice Seoul in a milisecond if it meant permanently destroying the DPRK.
It's still better to have nuclear weapons than not have them, in a majority of cases, if it makes sense and if you have the funds to get them.
I question if the funds would be better spent doing other civic works projects like nuclear power plants. I just don't know if they're as big of a deterrent as is claimed.
Besides, if the US was willing to sacrifice Seoul then why didn't they invade before the DPRK attained intercontinental capacity? If the US was willing to sacrifice its pawns so easily then surely they would have invaded before there was a risk of nuclear bombs hitting the US. I think it's because the US would lose if it invaded, because the Korean People's Army is the fourth largest in the world and properly trained and equipped. They're the true deterrent, I'm just not convinced that nuclear weapons really matter that much. I think it's overblown.
I think that the DPRK's military acts as a deterrent as well, probably more than anyone expects. And while I take the U.S. projections relating to military-related shit with a mountain of salt, I'm not sure the DPRK's military could "win" against the U.S. military, given the significant funding, material and technological advantages.
Though I am aware that the DPRK's military wouldn't be helpless, and the U.S. would suffer massive casualties.