Why Do People Make Art?

I think there are several reasons people make art. They do it to prove a point or show people their opinion on something. This is shown in art work like the famous painting of George Washington crossing the Deleware River. The picture glorifies Washinton and the troops making them seem ready and fit for battle. Another reason I think people make art is to simply express themselves. They could have an idea in their head for a while and then just let explode out int the world in their own way in a sculpture or a painitng or a poem or what have you.