[uoaei]

Art and science have their similarities. For instance, art is the exploration of the space of possible emotional truths, while science is the exploration of the space of possible statistical truths. Design and engineering are opposed to both art and science, in that the latter are open-ended explorations that by construction do not pre-suppose an end goal. Design is teleological, and engineering is just a means to bring designs to fruition. So examining the acronym closer we notice that even design is excluded from STEM which seems like a huge oversight -- you don't want engineers who are not practiced in designing functional, reliable systems...

Art is a very important part of the development of people as positive forces in society and civilization, and so presumably, if we assume good faith to explore this question, we could posit that people are reacting to the exclusion or at least de-emphasis of art education in conjunction with the typical STEM curriculum. The intention and goal is I believe best summarized in the famous quote from Jurassic Park: "your scientists were so preoccupied with whether or not they could, that they didn't stop to think if they should".