We can use the phrase why not? as a reply which shows that we agree to a suggestion or request: โ€ฆ You use why with 'not' in questions in order to express your annoyance or anger. Why not someone taller?

Understanding the Context

(relative) For which cause, reason, or purpose. That's the reason why I did that. That is why the sky is blue. Plastics are energy-rich substances, which is why many of them burn so readily.

Key Insights

Any organism that could unlock and use that energy would do well in the Anthropocene.