Chiaotzu, Yamcha and others in “Unfinished Business”

But why would Cell host a tournament?

Yamcha

Yeah, why? I mean if he wants to rule the world, why is he wasting time with this competition?

Trunks

Cell doesn't want to rule the world. He wants to destroy it.

Yamcha

Uh...?

Huh?

Trunks

The androids have never been interested in power. It's just that they find pleasure in causing fear and chaos. And Cell's no different. He's using this stupid tournament as a way to spread fear.