It's to persuade people to switch their vote in order to keep themselves safe.
Katie, Ciera and Tyson will DRAW ROCKS unless a unanimous decision is reached.
i don't understand why they drawn the rock, not Hayden & Monica. i don't think it was fair. can somebody explain it?
Yeah, and I assume it also adds another strategic element to it - i.e. Hayden/Katie/Ciera voting for Monica to try to get their true target Tyson out.