Have the Korean government massacred anyone since their democratisation?
You obviously don’t live in East Asia to realise why the South Korean government delay the handover. I will give you an important hint as much as national security: it saves them money. They get more bang for the buck. Same with the EU hosting American military bases. The EU isn’t being accused for “free-riding” for a reason.
South Korea get more than they bargained for which, not only deters North Korea and China, but also save them money. Why change the status quo overnight if it serves them very well so far?
Going back to the original matter at hand; yes, South Korea still exercise agency outside of the US influence in this matter. SK uses US more than the other way around.