North Korea only does so when it needs to exert political pressure externally.
The North Korean government is actually very smart. You can compare the North Korean government and the Iranian government, both countries are providing aid to Russia, but the results are completely different.
North Korea and Iran both gave Russia military aid, so what did they each get from Russia?
North Korea:
1, received technical assistance, satellite technology, missile technology, shipbuilding technology, drone technology have significantly improved;
2, thousands of containers of last century's nearly obsolete artillery shells, exchanged for foreign currency (Western media estimates that at least 20 billion euros sold).
3, the United Nations military sanctions against North Korea in name only. The sanctions have not affected North Korea's military trade with the permanent members, and then will not do so again in the future.
4, North Korea and Russia have formalized their military alliance. Add to that the defense treaty that North Korea and China signed in 1962. It now has the covenant of two military powers.
And what about Iran?
Sold some drones, which led to additional EU and US sanctions. And then what? No more then, nothing. Iran got scared and backed down from selling. So Iran got nothing but more sanctions.