Question

Why is it important to know the number of stars in the universe?

Answer 1

To, like, have your mind blown, dude! No, there are other reasons.

Explanation:

The number of stars does give astronomers a way of estimating the total amount of "normal" matter in the universe. This is important as normal matter only constitute about 4% of the total mass of the universe - the rest seems to be more hard to describe, dark matter and dark energy.