Street art is one of the most controversial art forms. In my opinion, street art is not tagging or vandalism, it makes a statement, says something profound and involves complex artistic design. Street artists perfect their skills and spend time creating their works. Still, there are some people who frown upon street art and won't accept it as an art form.
Many of the street artists make political statements with their art. Some enjoy the thrill of creating an artwork in a public space and enjoy watching the reactions. I'd say using streets to demonstrate your personal views is liberating.
Street art is diverse in every aspect you look at it. Artists have different styles, use different materials and express themselves in many sizes and shapes. You may not like a particular style, but you can fall in love with another.