why is it needed?

Answer 1

Where would we be without science?

We wouldn't understand our earth and its environment.
We wouldn't be communicating by computer and the Internet.
Our water and food might be adulterated or polluted.
We wouldn't have medicine, and our illnesses couldn't be treated.

Answer 2

Another reason is that scientific methods give us reliable ways of verifying or contradicting our beliefs concerning the world around us.

I hope this helps a little more. Thanks for asking.