High school kids are only a few years away from being able to vote. Some of them already can. There's tremendous pressure on them to pick a tribe that will identify them politically and increasingly and sadly, limit their social interactions. For those who are trying to get near-future voters into their tribe, destroying teens isn't something that matters to them, they just want the teen's allegiance, hopefully lifelong. If some commit suicide, that's a lost vote, but all of the other votes the tribe gains is worth that death. Afterall, there's no consequence to the tribe itself beyond the lost potential voter.