system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is Pi such an important number?
gpt
Because circles, circular looking things, rotations, and circle-looking curves are *everywhere*. If a given thing could include a circle even in the most tangentially abstract manner pi will find its way in to your calculations somehow. 

It's an important number because it's a fundamental facet of anything circular. Because we live in a world where we have things that curve pi will appear everywhere, making it pretty important. It's not that pi is important, but that circles are important.