*strums guitar* Why is it that authors make characters die?

Because that's how life works

To make us cry...........
Just joking, I think to make the story madami familiar to life, where death pervades regardless of time and person

Because we CAN

To make a good story

I'm pretty sure the real tanong is why do authors make our paborito characters die?
Or perhaps, why do authors make characters who we were just getting used to die?

that's a tanong the authors can only answer,but I would like to know why John Greene did that to Augustus Waters in TFIOS.

Here's a good artikulo to read on that
Talks about how Death is part of life, how death can be redemptive, how death engages the reader deeply, and sometimes death is the only possible resolution
link

Being a writer, I can assure you that this 4 segundo video is everything you need to know on the subject.