Question one is like asking "Why is it so?" about everything.
We need art to live ...ask any art teacher!!! no seriously, it is a
big question which has no slick answer. It has to do with the
whole human experience and is almost a "What is the meaning of life"
sort of question.. Look up a book on quotations and see what various
people have had to say on the subject.
Question 2 Art is free. but I suspect that was not what you meant.