Well we study it because, they think that maybe you'd be interested in stuff like The planet's, and the Universe, and etc. Also overall they try to help you understand that stuff like tornado's, hurricanes, and twisters. There's a lot more to it though, but there's a few examples right there as to why we learn it. :)
Because you need to know it. It can save your life for example I know that blood flows unless you cut the circulation so if I was bleeding out of my arm I would tie string around my arm above where I was bleeding, also if you ignore science it makes you ignorant and you will seem stupid to people who have basic knowledge.
Medicine; science has treated disease technology, science is the reason you have a computer/phone to ask this question knowledge of the universe, science is how we know that stars are and the size of the solar system As so we can keep moving forward and advancing in the world