Why does South Korea only promote selling everything?

Real estate, industries, technical secrets, and weapons.
Why is there such a desperate rush to sell the KF-21?
They should at least equip the Air Force fighter wings before looking at exports.
Why is there such a desperate rush to sell the K17 machine gun, a small arm developed after 45 years?
They should supply it to all Army units first before exporting it...
The KF-21 has barely produced one unit and is currently in the process of assembly and disassembly.
That is not "Gukppong" (extreme nationalism) or enhancing national prestige.
Please, let's focus on our own needs first.