A bit worrying!

[RetroPug]

They haven't done it because whilst their propaganda machine states otherwise, I imagine that their military analysts are well aware that whilst they could infilct massive civillian losses on S.Korea, the resulting counter attack would see their regime destroyed. It's mutually assured destruction, both sides have a huge amount to lose by actually going to war, hence why even live firing incidents and skirmishes have not escalated to full-scale conflicts.

The South actually has most to gain by keeping the Status quo though.

Think about it they're a properly developed country, if the North fell then they'd be totally swamped by millions from the North.
People that are basically brainwashed peasants with no useful skills to offer the Southern state.

The South would overnight become responsible for looking after 24 million refugees, it'd totally cripple their country.

Yes but equally the ruling elite in the North understand that in the aftermath of war they'd no longer be a ruling elite. These are people that have total, authoritarian power while their people starve.