Why doesn't the Demogoron just kill Will instead of kidnapping him?

Ch
2

I'm about the kidnapping of Will Byers in the Netflix series "Stranger Things" in the first episode of the first season. What is the use of the Demogorgon in the kidnapping of Will and later also of Barbara Holland's kidnapping. Does this simply serve as a kind of "plot device" or is there a deeper background that I'm overlooking here.

Ra

Spoiler

Barbara dies

However, Will is still alive, but is also on the verge of dying because he was locked in a cocoon by the Demogorgon. Hopper and Joice save him, but part of the "shadow monster" lives in him and so he sometimes gets to the other side even if he doesn't want to. And then it just continues with the second season.

Ch

I've seen the series too. I was just wondering why the Demogorgon kidnapped Will instead of killing him.