I have always been lead to believe that art should always try to evoke some type of emotional reponse by the artist. When I draw my response is always humorous. I like having a good laugh at my amateur art sometimes, because its fun. Art should, in my opinion, always be about finding joy and amusement with ones work. Even if its silly, or crude, or offensive art, the artist should always find each project a uplifting and engaging experiences.