Kdrama: Why did Ddol-bok and So-yi have to die?

The awesome website, kdramabeans, is my go-to site for step-by-step action of whatever kdrama I'm watching.  I'm one of the those people who looks at the end of the book soon after I start, and kdramabeans offers me that opportunity.  So I was intrigued when I read posting on episode 24 of "Tree with Deep Roots" and author questioned the deaths of the two young lovers, Ddol-bok and So-yi, 

I’m left to wonder why they couldn’t have just actually lived, and why that final scene we were shown truly couldn’t have come to pass. Did their deaths really change anything? Were those deaths necessary to propel the story? Not really.

First a bit of background -- this show is about the invention of the Korean alphabet by King Sejong in 1446 -- even before Columbus sailed the ocean blue.  This is a formidable feat, the making of a phonetic alphabet, easily learned by Koreans but also accessible to foreign students (I got the basics down in 59 minutes).  This drama centers around the ruling class's opposition to universal literacy. Ddol-bok and So-yi are servants who play important roles in the creation and dissemination of the language.  

Why do they die?  Could they lived modestly and happily ever after, having played a role in Korean history?  

Who knows what the authors were thinking, but I think all kdrama is metaphor, and therefore their deaths stand for a larger truth.  In this case the truth that the drama is exploring is the wisdom of the people.  The head of the opposition argues that the people will are protected from sophistry because of their lack of education.  They will be more vulnerable if they can read.  King Sejong doesn't buy that argument.  He replies that maybe sometimes, but not all the time, echoing Abraham Lincoln who famously said, "You can fool some of the people all the time, and you can fool all the people some of the time, but you can't fool all the people all the time."  In the meantime, the chance of literacy is a chance for dreams and hope.  

It is that dream for which Ddol-bok and So-yi are willing to risk their lives and die with pride.  Do they have to die? Well, of course not.  But their deaths signal the stake that working people have in literacy.  All working people have struggled for literacy, certainly including African Americans.  So I identify deeply with their commitment to this deep cause.  Ddol-bok and So-yi stand for the wisdom of the people in fighting for literacy and the chance to dream.