Well,as others have said,it provides food,sport and recreation........that is my 2c worth.
I suggest if you come onto a dedicated angling site and ask such a question (without any explanation,theory or justification) then you clearly have too much time on your hands!
Perhaps you should dedicate your energies to ridding the world of terrorists,rapists and pedophiles ( not sure how you justify them? ) before going after rec fisho's.
Just my opinion though........