STEM fields comprise science, technology, engineering, and mathematics. The modern world has been built on STEM subjects. Understanding and manipulating the world around us requires all these subjects.
Medical advances eg COVID vaccine research would not have been possible without scientific advances in biochemistry, mathematic advances in meteorological is giving us significant insights into the causes of and impacts from climate change and the human impact on our environment, engineering is developing ways for humanity to visit other planets and explore the cosmos so we can understand our beginnings and technology is improving how we communicate and articulate ideas and solutions. STEM can be applied to a variety of other topics including social geography, music and the arts, agriculture and a variety of other topics.
Compare HiLDA fields: history, language/literature, drama, art. Boys tend to prefer STEM while girls gravitate to HiLDA.