For better or worse (usually worse), it is your nature to feed on the life force of others. At least they die smiling. But killing people is messy and creates problems you could do without. It’s hard enough being a demon stranded in high school hell.
But you can rock! When things go your way, you are the star of the show. You can change people’s lives, as long as you don’t kill them. Anyone can rise to the top, if you let them get close. Just be careful they don’t turn on you.