Why can't Koreans have dual citizenship?

I've always been curious about this matter. Why can't Koreans hold dual citizenship? I understand that each country has its own laws and regulations regarding citizenship, but it seems like a rather restrictive policy, especially in today's globalized world. I mean, with the rise of cryptocurrency and other forms of digital assets, people are becoming more mobile and interconnected. Wouldn't it make sense for a country to allow its citizens to hold dual citizenship, thus fostering greater cultural exchange and economic opportunities? Or is there some deeper reason behind this policy that I'm not aware of?